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CULTURING ABALONE HALF-PEARLS

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					            CULTURING ABALONE HALF-PEARLS
                 The story of the New Zealand Eyris Blue Pearl™

                                 Pam Hutchins FGAA
                         Wide Bay Valuation Services, Bundaberg

ABSTRACT

  This paper provides information on the life history of the abalone, before describing
the technologies and methods used by New Zealand based Eyris Pearls to culture and
produce half-pearls from free diver harvested ‘wild’ stock of the New Zealand
abalone, Haliotis iris or paua. Criteria used to grade the pearls are also illustrated and
briefly described.

INTRODUCTION

  Attempts at culturing pearls in the
abalone have been in progress since
Louis Boutan’s pioneering experiments
in France during the early 20th century,
and La Place Bostwick's unsubstantiated
American experiments that he described
in rather euphemistic terms in 1936. By
the mid-50s, the Japanese researcher Dr
Kan Uno had developed culture
technology suitable for growing half-
pearls in several species of abalone. A
few years later, the Korean father and son team of Ki-Sun and Won-Ho Cho were
culturing half pearls and keshi pearls in Korean species of abalone. Most recently,
Canadian Professor Pete Fankboner has developed patented technology that is being
used commercially to culture half-pearls in the Californian H. rufescens or red
abalone. Quite independently, abalone pearls were cultivated experimentally in
Tasmania, until this culture ceased due to financial difficulties.

  New Zealand is presently the home of at least two successful abalone pearl culture
operations utilising the New Zealand paua, Haliotis iris (Martyn, 1784). These
commercial operations are Empress Pearl Ltd and the Eyris Blue Pearl Company.

  The story behind the creation of the Eyris cultured half-pearl, that is known
commercially as the Eyris blue pearl, is as remarkable as each individual product.
Roger Beattie, Managing Director of the Eyris Blue Pearl Company, has been diving
since 1978 and during that time spent seventeen years as a commercial paua diver.
He still holds the New Zealand record of 65 for the number of legal sized paua (over
125 mm) gathered in a single dive. Paua diving in New Zealand is restricted to free
diving, with no underwater breathing apparatus allowed.

 Over the years Roger Beattie has played an integral role in the management of the
New Zealand paua fishery. He was instrumental in getting a reseeding programme for
wild stock paua up and running, and became interested in farming paua.
  In 1989 he established the first ocean based abalone pearl culturing farm in the
Whangamoe inlet on New Zealand’s Chatham Islands, some 800 km east of
Christchurch. Until 1989 only natural abalone pearls were available for purchase, as
earlier research to culture pearls in these molluscs had been abandoned because of the
difficulties in both farming and nucleating abalone, a haemophilic univalve mollusc
that has a large central muscular foot. Two years later, catastrophic death of stock,
due to the combination of unusually heavy rainfall and protracted onshore winds
prompted the need to search for a second location. In 1994, another farm was
established in Akaroa Harbour on the Banks Peninsula. However, in 1996 an algal
bloom wiped out 50 per cent of the paua on the farm. To reduce the element of risk to
his stock Beattie decided to establish another pearl farm at Tory Channel in the
Marlborough Sounds. Farming in three geographically isolated locations helps to
minimise the risk of a disaster on any one farm.

ABOUT THE ABALONE

  The abalone is a univalve mollusc that is a member of a primitive group of marine
snails belonging to the class Gastropoda, sub-class Prosobranchia, order
Archeagastropod, and family Haliotidae. It is one of the largest gastropods.

  There are over 130 species of abalone throughout the world⎯all belonging to the
genus Halitotis. Around the world, countries whose waters host various species of
abalone refer to their indigenous species of Haliotis by local names such as abalone
(Australia and the USA), aulone (Mexico), perlemoen (South Africa), and paua⎯a
name given to the New Zealand abalone by the Maori.

  In New Zealand the Maori gathered paua both for food and its shell that was highly
prized both for decoration and jewellery. The New Zealand paua has the scientific
name Haliotis iris, meaning rainbow coloured abalone. These molluscs are only found
in the cool clear waters that surround the coastline of New Zealand. The paua is the
species of abalone that displays the greatest range of colours, and the strongest
iridescence from the nacre of any abalone.

Its anatomy

  The internal organs of the abalone are held under and within its univalve shell.
Figure 1 illustrates the major body parts of the abalone
                                                Each abalone has a large muscular foot with
                                                a diameter similar to that of the shell itself.
                                                The muscle of the foot has two functions.
                                                First, it creates the strong suction that
                                                permits the abalone to attach firmly onto
                                                rocky surfaces. Second, an associated
                                                vertical muscle column firmly attached the
                                                body of the abalone to the undersurface of
                                                its shell. The epipodium, which has a
                                                sensory function, consists of small tentacles
                                                that extend from the foot and project beyond
                                                the edge of the shell in the living mollusc.



Fig. 1. Gross soft tissue anatomy of the abalone.
After Cox (1962)



  As the surface of this epipodium may be smooth or pebbly in appearance, and its
edge may be either frilly or scalloped, it is the most reliable structure for
discriminating species of abalone. The internal organs of the abalone are arranged
around its foot and under its shell. This mollusc’s most conspicuous organ, its
crescent-shape gonad, which is grey or green in females and cream in males, extends
around the side opposite the respiratory apertures (pores) and to the rear of the
abalone. The head of the abalone has a pair of eyes, a mouth and enlarged pair of
tentacles. A long, file-like tongue (radula) in the mouth of the abalone is used to
scrape agal matter of ~3x3 mm size from rocks for food. A feathery gill, located next
to the mouth and under the shell’s respiratory pores, extract oxygen from seawater.
This water is drawn in under the edge of the abalone’s shell, and then it flows over the
gills and out though the pores. Waste and reproductive products (sperm or ova) are
also carried outwards in this flow of water. The mantle, which surrounds the foot and
body of the abalone and is closely adapted to the inside of the shell, is responsible for
the secretion of the shell and its lining of iridescent nacre.

  Since the abalone has no obvious brain structure, it is considered to be a primitive
animal. However, it does have a heart on its left side and bluish coloured blood flows
through the abalone’s arteries, sinuses and veins, assisted by the surrounding tissues
and muscles.
Fig. 2. Gross anatomical features of the abalone shell, RHS - external view, RHS internal view.
Adapted from Howarth (1978)

  The univalve shell of the abalone has an oval shape, but is more pointed towards the
head of the mollusc. The external surface of the shell (Fig. 2A) is characterized by the
presence of a series of respiratory apertures that close towards the rear of the shell,
and a spiral shaped apex that is located to the rear of the shell. Concentric growth
rings are readily visible towards the front of the shell. Internally (Fig. 2B) the shell is
lined with nacre, of variable iridescence, which is patterned by the scar of the muscle
attachment to the inside of the shell, and the internal manifestation of the whorl of the
shell’s apex. A flattened columella extends along the rim of the shell from the rear of
the shell to the region where open respiratory apertures are readily visible.

How it reproduces

  When spawning, eggs and sperm are released from the gonads of female and male
abalone through a series of respiratory pores (apertures or holes) in the shell through
which the abalone draws oxygenated sea water to its gill. This is known as broadcast
spawning. One 37 mm abalone may spawn 10,000 eggs or more at a time, while 21
cm abalone may spawn 11 million or more. Spawning is usually controlled by factors
such as water temperature or the length of the day. Additionally, the presence of eggs
and sperm in the water may stimulate other abalone to spawn, thus increasing the
chances of fertilization.

  Fertilized eggs hatch as a microscopic,
free living larva that drift with the currents
for about a week. Then the larva settles to
the bottom, shed their swimming ‘hairs’
(cila), and begins to develop into their
shell-bearing adult form. If a suitable
habitat is located, the abalone may grow to
adulthood in the steps illustrated in figure
3. However, the chance that an individual
larva will survive to adulthood in the
‘wild’ is very low.
                                                     Fig. 3. Life cycle of the abalone
  It is interesting to note that while the sexes of the abalone are quite separate, they
can be identified as either males or females (based on the colour of their gonads) as
soon as they are about 25 mm in size (when the gonads have begun to develop).

Age and growth

  Determining the age of an individual abalone is difficult, for unlike the hard parts of
some animals the abalone shell has no regular pattern of growth marks or bands
suitable for assigning age. However, it has been estimated that aquarium-bred juvenile
abalone grow at the rate of 2-3 cm or more per year for the first two years. Tagging
studies have provided some estimates of the rate of growth of larger abalone in the
wild. For example, red abalone (H. rufescens) are mature at 4-5 cm, after which
growth begins to slow with age. Therefore, an 18 cm red abalone may be 7-10 years
old, while one only 2 cm longer may be 15 years of age or older.

ABALONE HALF-PEARL CULTURE

Production of stock

  Stock suitable for implantation are obtained both from the ‘wild’ and from spat
culture.

  Spat (very young abalone) are purchased either from privately owned or
government controlled hatcheries, where they have been raised from fertilized ova in
a series of special hatchery tanks. The smaller paua (those of 5 mm) size are kept in
the special tubes so that they can attain a good size that will help their subsequent
survival when replanted into the ‘wild’ (ocean waters).

  Hatchery bred juveniles are returned to the ‘wild’ (their natural environment) in a
process known as ‘reseeding’. Subsequent growth to maturity in these somewhat
protected environments will give the juveniles a good chance of survival and growth
in the ‘wild’, for their food will be plentiful and they are somewhat protected from
their natural predators. These factors should ensure fast growth, and this helps to
replenish levels of ‘wild’ stock in the waters around New Zealand.

  Throughout their life in the ‘wild’, abalone have to contend with a variety of natural
predators—with eggs and larvae being eaten by other filter-feeding animals; juvenile
abalone that are nocturnal (active at night) often becoming natural prey for crabs,
lobsters, octopuses, starfish, the cabezon fish, the bat ray, and of course sea otters;
while mature abalone are attacked by a range of parasites that include shell boring
worms, boring barnacles polycheaete worms, and various species of polydora worms.
To survive in the ‘wild’ abalone need to hide under water, firmly attached to rocks
and in crevices within masses of rock. In addition, an algal bloom can suffocate the
abalone and destroy a whole population both in the ‘wild’ and in the waters of a pearl
culture farm.

  An annual quota of ‘wild’ abalone is allowed to be harvested from the ocean waters
surrounding New Zealand, near the rocky shoreline and on the rocky shallows of the
continental shelf. For Eyris Blue pearls this annual quota is currently 23 tonnes.
THE CULTURE OPERATION

Location of farms

                                          Eyris Blue Pearls operate five pearl culture farms
                                          at geographically isolated locations (Fig. 4) in the
                                          cool waters that surround New Zealand. The
                                          company’s first farm was established in 1989 at
                           Wellington     Whangamore Inlet on the Chatham Islands. These
                                          remote islands lie some 800 km to the east of
                                          Christchurch. The second and third farms were
                                          established on Banks Peninsula to the south of
                                          Christchurch (Fig. 5). Presently these farms act as
                                          holding areas for new stock before they are moved
                                          further out to sea for grow-out following
                                         implantation.
 Fig. 4. Location of Eyris Blue Pearls
 pearl culturing operations.



The fourth farm, which is located at
Tory Channel in the Marlborough
Sounds on the north of New Zealand’s
South Island, is now in full production.
The latest farm is located in Wellington
Harbour on the south of the North
Island. Presently, this farm is being used
to cultivate seaweed to feed the abalone.

                                               Fig. 5. Pristine waters of Akaroa Bay on the
                                               Banks Peninsula, site of one of Eyris Blue
                                               Pearls’ pearl culturing operations,


Selection of stock

  It is considered that ‘wild’ abalone that
grow naturally, or are derived from reseeded
hatchery-bred spat have good genetic
diversity, and are ideal for producing cultured
pearls. This fact is highlighted by the strong
and vibrant iridescent colours that can be
observed (Fig. 6) on the nacre that lines the
shells of ‘wild’ abalone . Abalone chosen for
collection as ‘mother’ abalone must neither
have any evidence of marine borers in their
shell, nor display any evidence of disease or               Fig. 6. Characteristic iridescent nacre
                                                            of the ‘wild’ H. iris.

deformity. Usually this is the case of only one mollusc in twenty that is inspected in
the ‘wild’ and deemed to be suitable for use as a producer of a cultured pearl. When
harvesting the license holder’s annual quota of abalone from the ‘wild’, divers do not
use air tanks. Instead, these divers use free diving technology and must have very
good lung capacity. It is thought that this conservative collection philosophy gives the
abalone a more than reasonable chance of not being fished out.

  The legal size of the ‘wild’ abalone that can be fished for stock is a shell length of
125-135 mm. This size equates to an age of 4-5 years. It is believed that this size
restriction gives more young ‘wild’ abalone a chance to attain adulthood and become
the future ‘mothers’ for pearl cultivation.

                                           ‘Wild’ abalone are harvested from
                                         designated areas where they are most active
                                         and prolific. Special non-injurious tools are
                                         used to prize the abalone from their
                                         underwater rocky substrates without damaging
                                         either their shells or delicate soft tissues. A
                                         special      slightly    curved    plastic   tool
                                         (Fig. 7 ) is used to slip under the front of the
                                         abalone. To avoid damage it is important that
                                         divers be aware of which end to lift the
                                         abalone from the rocky surface to which it is
                                         firmly attached. This specially designed
                                         plastic lifter will neither harm the animal nor
Fig. 7. Special tool for removing        damage the flesh of the animal and so cause it
abalone from rocks.                      to bleed to death (as abalone are
haemophiliacs =                          bleeders).

  It takes about 3 years before the abalone reaches adulthood. At this stage, adults are
tagged with a notch on the shell and a red tag cemented to the outside of the shell

  When the harvested abalone are brought to the surface, they must be stacked
carefully so that they do not stick together (by their muscular feet). If this occurs, this
causes great problems for those attempting to separating them.

The pearl farm

  The long-term health of captive abalone is affected by a variety of factors that are
related to the seawater in which the abalone are kept. These factors include the
chemical composition, temperature, pH, oxygen and nitrogen levels, and flow rate of
the seawater. All of these factors play an important part in the health and growth of
the abalone, and of course, the ability of the abalone to produced quality nacreous
pearls.

  Efficient farm management requires the systematic monitoring levels of these
factors in the water associated with the farm site, and the gathering and dissemination
of this information to local and regional councils so that these regulatory bodies are
aware of and can monitor any environment issues that may develop.

  If the water temperature fluctuates greatly between 6 and 21 °C, then this will affect
the colour of the nacre that the abalone will secrete; it will determine the layering of
both conchyolin and nacre; and will modify the intensity of colour in the secreted
nacre. This well illustrated Akaroa Harbour, a harbour that has highest rise and fall of
sea water temperature of any pearl culture site in New Zealand.

  All cool water abalones are slow growing and can live up to 6 years of age if
predators or disease do not kill them first. To improve the survival rates of their
implanted abalone, Eyris Blue Pearls use specially design barrels to house the abalone
involved in their pearl culture. These barrels (Fig. 8) are manufactured from black,
medium density polyurethane plastic which resists the growth of fungus on its
surfaces. Each barrel has plastic mesh its top and bottom, and flow-through mesh
vents in its sides. The inside of each barrel is divided into four sections in which the
abalone are housed and are free to move around within a relatively restricted area. If
sea snails enter barrels containing abalone, these snails will remove any adherent
sponges that may start to grow on the abalone and so threaten their health.




                                   Fig. 8. A UV stabilized medium density polyurethane
                                   barrel, with water circulation vents, in which abalone are
                                   kept during pearl culture. Each barrel is specially
                                   conditioned, before paua are housed in them, by soaking
                                   the barrels in seawater for one month. This removes the
                                   plastic taste from the barrel, as abalone can not be housed
                                   successfully in new unconditioned barrels.




  Good hygiene is very important if the abalone confined to these barrels are to
maintain health and nacre secreting ability. Consequently, the abalone must be
regularly removed from their barrels, their shells hand scrubbed to remove
contaminants and parasites, and then checked for any infections⎯while the barrels
are being cleaned by high pressure sea water to remove any debris, or adherent
seaweed and other sea life.

  While secured in these barrels, the implanted abalone will continue to spawn, with
their fertilized larvae floating away to hopefully settle, grow naturally, and naturally
Reseed the area in which the barrels are located. If this natural spawning tends to be
irregular, then the farm often will introduce some peroxide into the water to stimulate
the spawning of the abalone naturally.

The nucleation process

  As some parts of this process are kept as closely guarded commercial secrets, only a
very general description of this process can be provided.
  One month before the nucleation operation is due, ‘wild’ abalone of legal size are
harvested by free divers. As the New Zealand Government has placed a quota system
(bag limit) on the number of abalone that may be taken from the wild each year, each
farm has to operate within the constraints imposed by this conservation-based system.
This quota system prevents over fishing of the abalone. Abalone divers are specially
trained so that they minimize injury to the abalone during capture and removal from
their natural habitat. Following capture, the abalone are brought to the surface and
placed in plastic barrels in a suitable holding area. The paua are nucleated on board a
specially developed pearling vessel.

  At the time of implant, the now-acclimatized
abalone are removed from its holding barrels and a
small hole or a series of small holes must be
atraumatically drilled through the shell of each
abalone to facilitate placement of a pegged implant
under the mantle of the abalone. During this
implant operation care must be exercised to ensure
that the soft tissues of the abalone are not damaged
in any way⎯for abalone are hemophiliacs and will
bleed to death if cut.

                                                 Fig. 9. Retraction of the body and mantle
                                                 of the abalone to allow the pegged inplant
                                                 to be inserted in a hole drilled through the
                                                 shell of the abalone.

  The implants, which are of proprietary design, are manufactured from moulded
white plastic. They have a somewhat flattened hemispherical shape, diameters of from
8-14 mm, smooth outlines, a retaining peg projecting from the base of the implant,
and they must have no projections or rough areas that can injure the mantle tissues of
the abalone. No adhesive is used to maintain the implant in the shell.

                                       Two implant locations seem to be used: one
                                       located around the periphery of the abalone’s
                                       shell and a second located deep within the shell
                                       near the shell’s internal whorl.

                                       Once the implant operation is completed, the
                                       ‘mother’ abalone are returned to their culture
                                       barrels (Fig. 10). Each barrel is given a number
                                       and a record is kept of the number of implanted
                                       abalone contained in each barrel.
 Fig. 10. Implanted abalone attached
 to the wall of a culture barrel for
 grow-out.

 Unlike pearl ‘oysters’, each abalone can only be nucleated once. One to five beads
are nucleated in each abalone, depending on its size. Sizes of cultured half-pearls
yielded after an appropriate grow-out period range from diameters of 6 – 20 mm.
  Eyris cultured half-pearls
are farmed (grown out) for a
minimum of two winters and
two summers in black high
density polythene barrels that
are suspended from long-
lines off shore (Fig. 11).
During the time of grow-out
the abalone must be regularly
fed with a proprietary mix of
freshly harvested seaweed.
Its is a fact that the abalone
are very fussy and are indeed
gourmet eaters, for they like
to eat seaweed that humans
                                    Fig. 11. On the pearl farm in Matt White Bay on the
also find tasty and palatable.      Banks Peninsula the culture barrels are suspended
                                    under water from ropes suspended from buoys in waters
                                    with good tidal flow.

  Seaweed that produce the best display of colours in abalone nacre include an
appropriate mix of :

       •   Macrocystis pyritera or giant kelp (Fig. 12A)⎯ a large brown seaweed
           that has big leaves and a bulky, slightly coarse texture,
       •   Gracillaria (Fig. 12B), a fine filamentous red seaweed that has a fine
           texture, and
       •   Ulva, or green seaweed




      Fig. 12. Seaweed suitable for feeding implanted abalone. A – giant kelp, B – red seaweed

  The implanted abalone will consume up to 50 per cent of their body weight of
seaweed each week, with their mix of food varying from week to week. Together with
water temperature, pH and salinity of the seawater, it is the composition of mix of
seaweed that is fed to the implanted abalone that determines the quality and
iridescence of nacre secreted by the abalone.

  To maintain a constant supply of the seaweed, this must be collected from the
shorelines after a big storm, or deliberately harvested from kelp farms. Collecting
shore-washed seaweed means that at that time ‘all hands must be on deck’ to collect
seaweed, cut it into appropriate sizes, and then freeze or dry it for later use when no
shore-washed seaweed is available for collection. Dried or frozen is simply
rejuvenated by immersing it in fresh seawater. This rapidly brings back the shape and
bulkiness of the kelp.

  Some fine seaweed that grows on the culture barrels is also harvested and fed to the
implanted abalone. With respect to abalone pearl culture it is important to remember
that without reliable supply of quality seaweed, pearl farming would not be a viable
operation.

  During their life on the farm the paua
 are cared for by a dedicated team of
aquaculturists. Each week, regardless of the
weather the pearl vessel pulls up at the farm
and the barrels that house the paua are lifted
gently from the water. The paua are checked
to see that they are in good health, their
barrels cleaned, then in goes their favourite
food, a variety of fresh seaweed.

                                               Fig. 13. Routine inspection and feeding of
                                               implanted abalone

 With respect to the length of culture it is important to remember that in the winter
months the mantle cells of the implanted abalone lay down (secrete) predominantly
dark organic brown conchiolin. In contrast, the summer months are the time when the
implanted abalone lay down translucent layers of nacre over the top of and within the
previously deposited layers of conchyolin. One of the major factors controlling
successful half-pearl cultivation in abalone is to ensure that the nucleation takes place
at the correct period of each year, and that the pearls are harvested at that time of the
year when best quality nacre is being secreted in thickest layers.

How nacre is deposited

  Following implant, the abalone’s mantle starts to form the half-pearl by first
secreting the first layer of conchyolin - a brown coloured organic layer – initially on
the side of the implant and then as a thin layer covering the top of the implant. This
conchyolin becomes the mortar into which layers of nacre are subsequently deposited.
This sequence of deposition of conchyolin followed by aragonitic nacre is repeated
successively to create the pearl. The content of conchyolin in the pearl is critical with
respect to the strength of nacre, for the ideal incorporation of 1-5 wt % organic matter
into the nacre will create a pearl that has a fracture toughness x 3000 greater than that
of pure aragonite (CaCO3).
Harvest

                                                   Up to 36 months, and thousands of
                                                layers later, the resulting cultured half-
                                                pearl presents a lustre and iridescence
                                                that is almost magical to behold. The
                                                pearl harvest is a time of great
                                                excitement for the Eyris Blue Pearl team;
                                                the culmination of a minimum of two
                                                years work for everyone involved. Will
                                                this be a good harvest, or a great harvest?
                                                Will the next paua contain a perfect
 Fig. 14. The pearl farm work boat in action     iridescent, brilliantly coloured, gem
 removing barrels of implanted abalone from      quality blue pearl? Nature has kept her
 the sea.
                                                 pearly secret safe throughout this period,
only at the pearl harvest are the results of her work revealed.

All staff on the farms work long hours, even in bad weather, for the harvest must still
go ahead at a predetermined time when nacre secretion is at optimal levels. The grow-
out areas are accessed by sea by specially designed work boats that are equipped with
four hydraulic arms that are used to pull the barrels from the water, for the purposes
of feeding, cleaning or harvesting.

  The barrels that are brought to the surface will have tags attached that show the area
where the abalone came from, the diver who harvested the abalone, and barrel
number, and details of when and where the abalone were implanted. Following the
harvest of abalone from a barrel, the data is transferred both to the farm and head
office so that it can be stored for bookkeeping, record and research purposes.

 At harvest (Fig. 14), the implanted abalone is
sacrificed, the valuable flesh of the abalone is
removed from its shell and marketed to Asian
gourmet food markets. The residual shell and its
attached half-pearl/s are returned to shore where
the cultured blisters are processed into saleable
half-pearls, while the residual shell is on-sold
for inlay and decorative purposes.




                                                      Fig. 15. Harvesting pearl bearing H.
                                                      iris or paua.
Removal and processing of pearls



                                                Fig. 16. The results of several years
                                                cultivation.
                                                LHS - a 20 mm nacreous blister that took
                                                three years of cultivation in an abalone of
                                                small size.
                                                RHS - multiple smaller blisters in a larger
                                                abalone that will require two years of
                                                cultivation.




Several manufacturing steps are required to transform the cultured blisters within the
shell of the abalone (Fig. 15) into saleable pearls. These steps involve:

1. The blister pearl is cut from the shell using a diamond saw.
2. The blister and adherent shell are split to facilitate removal of both the plastic
   implant and the ‘crusty’ layer of residual shell from the nacreous blister.
3. The insert is removed from the blister.
4. The nacreous blister is cleaned by washing it and blowing it dry with an air gun.
   This deliberate use of high pressure air will rapidly detect any weaknesses in the
   nacre.
5. All nacreous blisters making it through to this stage, are then measured with a
   micrometer to determine the thickness of their nacre.
6. Blisters that attain the required thickness 0.3mm and over will be manufactured
   into and marketed as Eyris Blue Pearls™. In contrast, blisters having nacre of less
   than 0.3 mm thickness will be manufactured into and marketed as Pacific Blue
   Pearls™.
7. The blisters are then filled with colourless resin in two stages: a first stage that is
   allowed to harden for 48 hours; then a final fill before the blister is trimmed and a
   base added.
8. The filled blister is then shaped (by removing excess nacre) to produce a
   symmetrical girdle of the optimal diameter and thickness. The machinery used to
   shape and polish the soon-to-be half-pearls are modified lapidary equipments.
   Dopping ensures that the finished pearls will be as symmetrical as possible.
9. The filled, shaped blisters are then dried prior to their finishing by adhering a base
   to the blister. Paua shell mother-of-pearl backs are produced by a core drill. Any
   adherent shell is removed by using 80 grit abrasive to only expose nacre. A 100
    grit abrasive wheel is then used to regrind the girdle after the backing has been
    cemented to the filled blister. A 600 grit polish is used for the final finish of the
    girdle to ensure that the pearl has the right thickness for setting. Residual
    conchyolin is removed from the external nacreous layer of the pearl by the careful
    application of tripoli on a rotating polishing mop.
10. The finished pearls are then sorted into commercial sizes and shapes (Fig. 16)




   Fig. 17. Top -    Common commercial sizes of round Eyris Blue Pearls ( 10-15 mm).
            Bottom - Range of available shapes of Eyris Blue Pearls L to R – round, heart,
                     oval, drop

GEMMOLOGY

  Albalone half-pearls, cultured by Eyris Pearls, have the following general
gemmological characteristics:

Chemical composition: Nacre that is formed from aragonitic calcium carbonate,
                         brownish conchyolin, and water
Hardness (Mohs scale): 3 – 4½
Fracture:                 Conchiodal to hackly
Specific Gravity:         2.6 – 2.8
‘Spot’ refractive Index : 1.52 to 1.65

The structure of the nacre of these cultured half-pearls is illustrated in figure 17




                                                  Fig. 18. SEM photomicrograph of the thin, even
                                                  layers of aragonitic nacre that are found on an
                                                  Eyris Blue Pearl™.
  The thickness of each succeeding layer of conchyolin and nacre, and the pattern in
which they are laid down, is dependent on such factors as the genetic makeup and
health of the individual abalone, its food (seaweed) and the environment in which the
pearl has been cultivated.

GRADING

  Eyris Blue Pearls™ are graded for sale into categories of Gem, A and B grade by an
exacting process that involves detailed consideration of the individual pearl’s colour,
surface and lustre (See Box A). Shape and dimensions have no influence on the
assigned grade. Detailed criteria for quantifying lustre (into categories of mirror,
reflective and soft), surface (into categories of smooth, visible, and textured), and
colour (into categories of green gold pink brights or subtles, green blue brights or
subtles, blue green brights or subtles, blue violet brights or subtles) have been
published in print and electronically (at bluepearls.com) as The Eyris Blue Pearl
Grading System.

According to the published grading system:

Gem grade pearls must be eye-catching; it must have ‘the look’. A gem quality pearl
must have vibrant colour, iridescence, good character, no obvious faults, no scratches,
and no surface imperfections that detract from the quality of the pearl. It must have
great lustre and a smooth surface.

A grade pearls must have a mostly smooth surface and be of good quality with good
lustre and few obvious faults. Any imperfections must be slight and not detract from
the attractiveness of the pearl. The pearl must have good colour, iridescence and
character.

B grade pearls, although still good useable pearls, do not display the same
characteristics as 'Gem' and A grade pearls. The surface of a 'B' grade pearl is mostly
not smooth and can be visibly textured, while the lustre of the B grade pearl can range
from mirror to soft. There may be some surface roughness and the colour may not be
as vibrant or eye-catching as 'Gem' or 'A grade pearls.

C grade pearls are those that fall below the three standards set above. They may be
reject pearls or marketed as Pacific Blue Pearls. A marketable 'C' grade pearl may
have major faults and will require the use of innovative jewellery setting. Generally
they will lack character and it will be easy to see why they do not make the grade.

Interested gemmologists should consult The Eyris Blue Pearl Grading System to
become competent in the use of this grading system.
THE LAST   STAGE IN THE PROCESS

  As the last stage in producing this attractive cultured abalone half pearl, the pearl’s
history is stored in a computer system that creates a unique identification system for
each pearl. What is recorded and available to a future customer on a once only basis is
information about: who was the diver who fished the ‘mother’ abalone; the date and
area where the abalone was harvested from the ‘wild’; and the size and quality of the
pearl that was recovered from the shell. This unique identity is passed onto each
customer, via the special certificate that is issued with every Eyris Blue Pearl™ sold.
Simply put, if the pearl doesn’t have this certificate, then it is not an authentic Eyris
Blue Pearl™

Acknowledgements:
The author wishes to thank Roger Beattie and Shirley Went of Eyris Blue Pearls,
Murray Brereton of Akaroa Blue Pearls, and various State and Commonwealth
Departments of Fisheries and Industry throughout Australia.

Address for correspondence:
Pam Hutchins
P.O. Box 298
Bundaberg Q 4670
email: pamhutchins@bigpond.com
                      BOX A


 LUSTRE



          Smooth      Visible         Textured


SURFACE



             Mirror      Reflective   Soft




COLOUR
Websites consulted:

www.bluepearls.com
www. bluepearls.com/members/training.cfm
www.abalonenetwork.org/scan_science
www. niwa.cri.nz/pubs/au/28/paua-parasites
www. abalone.net/guide/abanat1.htm
www.islandpearls.net/2r2.htm
www.dpiwe.tas.gov.au/inter.nsf
www.rsnz.org/publish/nzjmfr
www.usabalone.com/offering/business.html

				
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Description: CULTURING ABALONE HALF-PEARLS