Unit One - Field Methods
3. Geological Mapping
Vocabulary

Demarcation: The setting or marking of boundaries.

Lithology - A systematic description of rocks, interms of mineral composition and texture.

Mylonite:   A hard, coherent, often glassy-looking rock that has suffered extreme mechanical deformation and granulation but has remained chemically unaltered; appearance is flinty, banded, or streaked, but the nature of the parent rock is easily recognized.

Breccia:   A rock made up of very angular coarse fragments; may be sedimentary or may be formed by grinding or crushing along faults.

Gouge:   Soft, pulverized mixture of rock and mineral material found along shear (fault) zones and produced by the differential movement across the plane of slippage.

Andalusite:   Al₂SiO₅   A brown, yellow, green, red, or gray neosilicate mineral crystallizing in the orthoghombic system, usually found in metamorphic rocks.

Phlogopite:   K₂(Mg, Fe(II))₆(Si₆Al₂O₂₀(OH)₄    A yellow-brown to copper colored mineral of the mica group occurring in disseminated flakes, foliated masses, or large crystals; hardness is 2.5 – 3.0 on Hohs scale, and specific gravity is 2.8 – 3.0.  Also known as bronze mica or brown mica.

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