Illite

Illite

A potassium-bearing mica-like clay mineral that is a product of hydrothermal alteration. It commonly replaces feldspars and other alumino-silicate minerals and it forms above ~220°C. It also reflects a weakly acidic pH condition in hydrothermal fluids.

Geothermal Glossary

Word of the Week – Geyser

Word of the Week – Geyser

Geyser A rare type of hot spring that periodically discharges a fountain of hot water and steam (or sometimes just gas).

Word of the Week – Gneiss

Word of the Week – Gneiss

Gneiss Metamorphic rock that forms under intense pressure and high temperature and that is made of quartz, feldspar, amphibole and mica. Gneiss represents the highest grade of metamorphic rock, which is characterized by alternating bands of dark and light-colored...

Word of the Week – Granite

Word of the Week – Granite

Granite Light colored, coarse grained, intrusive rock with a felsic (silica-rich) composition that is mostly made of quartz, sodium and potassium-bearing feldspar, and plagioclase. Minor amounts of other minerals can include mica (muscovite, biotite), hornblende,...

Utah FORGE

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