Primary minerals form from magma deep within the earth.
Secondary minerals form during weathering at the surface of the earth.

• translucent, often milky
• irregular surface, not planar
• very hard

Composition: SiO2

Found in: many rocks, esp. light-color (felsic), sandstones.

• platy, sheet-like
• black (biotite) or clear (muscovite)
• soft, can be peeled

Composition: (Al, Si + O) with K

Found in: many igneous and metamorphic rocks.

• angular, sharp crystal faces/edges
• tan to brown, pink, whitish

Composition: (Al, Si + O) with K

Found in: many igneous and metamorphic rocks.

• angular, sharp crystal faces
• black or very dark green

Composition: (Al, Si + O) with Mg, Fe

Found in: dark (mafic) igneous rocks.

• dull, seldom crystalline
• dull red (hematite) to yellow (goethite)
• usually soft, dense masses

Composition: Fe(O,OH)Found in: sedimentary rocks; saprolite.

• dull; seldom crystalline
• whitish to grey
• soft

Composition: (Al, Si, O)

Found in: sedimentary rocks; saprolite.

ROCKS: Assemblage of minerals; a fixed proportion of various minerals present give characteristic appearance & properties.Igneous rocks form from the cooling of magma.
Metamorphic rocks form from alteration (pressure, heat).
Sedimentary rocks form from cemented sediments in the ocean floor.

• Light colored (mafic); fine to large crystals.
• Uniform texture (no banding).

Composition: Largely quartz, feldspar; some mica.

Found in: Intrusive bodies in Piedmont (Stone Mt).

• Dark colored (mafic); fine to very fine crystals.
• Uniform texture (no banding).

Composition: High in ferromagnesian minerals (hornblende, augite).

Isolated occurrence in Piedmont (seafloor remnants deposited during orogeny).

• Intermediate to dark colored; fine to coarse crystals.
• Finely banded (foliated), light and dark.

Composition: Commonly mica, with quartz, feldspar.

Formed from metamorphosed sediments; common in Piedmont, Blue Ridge.

• Intermediate to light color; medium – coarse crystals.
• Coarsely banded, fine dark bands/coarse light bands.

Composition: Quartz, feldspar, mica.

Formed from metamorphosed granites or sandy marine sediments; common in Piedmont, Blue Ridge.

• Whitish to light grey; few crystals; may contain fossils.
• May be coarsely or finely banded, or massive.

Composition: Calcite, with mixture of clay minerals.

Formed in off-shore marine environments; common in Valley & Ridge, parts of Coastal Plain.

• Various colors (grey, brown, tan, reddish).
• Feels sandy when rubbed.
• May or may not be banded.

Composition: Quartz with some oxides.

Formed in near-shore marine deposits; common in Valley & Ridge, parts of Coastal Plain.

• Usually grey/brownish grey (also tan to red).
• Finely layered (foliated); often soft, easily broken (siltstone).

Composition: Clay minerals with accessory minerals (oxides).

Formed in near-shore marshes, or in deep-water marine environments; common in Valley & Ridge.