• Rocks that have changed due to
temperature and pressure increases or that
undergo changes in composition.
• Can be formed from igneous, sedimentary,
or other metamorphic rocks.
Yellow areas are
rocks are formed.
Heat and Pressure
• Rocks underneath Earth’s surface are under great
pressure from overlying rock.
• Mineral grains are flattened.
• Sometimes minerals exchange atoms with
surrounding minerals and new or bigger minerals
Heat and Pressure
• Igneous rock granite can be changed into the
metamorphic rock gneiss.
• Depending on the amount of pressure, one type
of rock can turn into several different
• Shale turns into slate, slate into phyllite, then
schist and eventually gneiss.
Classification of Metamorphic
• Classified according to their texture.
• Foliated Rocks
– When mineral
grains line up
rock has a
• Examples of foliated rocks
are slate and gneiss.
• Slate: forms from sed. rock shale. Minerals in shale are
arranged into layers when exposed to heat and pressure.
Slate is easily separated along these foliated layers. The
minerals in slate are so tightly packed that water cannot
pass through them. Used in patios, stepping stones and
• Gneiss forms when
granite and other rocks
are changed. Quartz,
feldspar, mica, and other
minerals in granite aren’t
changed much, but they
are rearranged into
• No banding occurs. The minerals change, grow,
and rearrange, but they don’t form bands. This
produces nonfoliated texture.
• Examples include sandstone, and marble.
• Quartzite: composed mostly
of quartz. Quartz under
pressure and heated, turns
to quartzite. The only
change that has occurred is
the size of the mineral
• Marble: forms from the sedimentary rock
limestone, which is composed of calcite. Calcite
crystals give the crystals their glassy, shiny
luster that makes is popular for sculpting.
• Marble contains several other minerals besides
calcite. Hornblende and serpentine give marble
a greenish tone, hematite makes it red.