Contains 15 specimens, approximately 1 1/2" x 1 1/2",
number-coded in a compartmented container
METAMORPHIC ROCKS
Metamorphic rocks may be formed by different processes. Generally they are recrystallized
in the solid state by pressure and heat and may be influenced by the introduction of
chemically active solutions. Igneous, sedimentary, and pre-existing metamorphic rocks may
become metamorphic rocks. The change may be partial and some of the original
characteristics retained, or it may be so complete that new minerals are formed and the
texture altered.
FOLIATED ROCKS
1. GNEISS may be formed form granites or sedimentary
rocks and typically shows layering of mica, quartz and feldspar.
2. GRAPHITE SCHIST is composed of the mineral graphite having a layered texture.
3. MICA SCHIST is composed of small layered flakes of muscovite or biotite.
4. GARNET SCHIST is composed primarily of small flakes of mica with larger crystals of
garnet.
5. CHLORITE SCHIST is composed almost completely of the mineral chlorite with a layered
texture.
6. SLATE is a metamorphosed shale. It has an extremely fine texture and splits cleanly
along its rock planes.
7. PHYLLITE is intermediate between schist and slate. A silky sheen is characteristic of
phyllite.
8. SOAPSTONE is a rock rich in talc. When layering is apparent, it is called talc schist.
NON-FOLIATED ROCKS
9. QUARTZITE is a metamrphosed sandstone which is
partially recrystallized.
10. SERPENTINITE is a metamorphosed serpentine rock derived from the alteration of olivine
and pyroxene or impure limestone.
11. EPIDOSITE is composed primarily of the minerals epidote and quartz.
12. MARBLE is a recrystallized limestone (calcite).
13. SERPENTINE MARBLE is a recrystallized limestone containing some impurities.
14. AMPHIBOLITE consists of amphiboles and plagioclase feldspar. If may also show
foliation.
15. HORNFELS is usually a fine-grained non-foliated rock and may retain some of its
sedimentary structure.
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