GEOLOGY - CHAPTER2 (HORNBLENDE) Flashcards
is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in
igneous and metamorphic rocks.
Hornblende
got its name from the German word horn and blended
which means to blind or to dazzle. The meaning of the name is any dark prismatic mineral that occurs in ores
but does not contain any recoverable metals.
Hornblende
is a common constituent of many igneous and metamorphic rocks such as granite, diorite
and basalt. It crystallizes in preference to pyroxene minerals from cooler magma that is richer in silica and water.
Hornblende
is a rock-forming mineral that is an important constituent in acidic and intermediate
igneous rocks such as granite. It is also found in metamorphic rocks such as gneiss and schist. A few rocks consist
almost entirely of hornblende.
Hornblende
as a group are relatively easy to identify. The diagnostic properties are their dark
color and the directions. The angle between the cleavage planes and hornblende’s elongate habit can be used
to distinguish it from augite and other minerals that have a short blocky habit and cleavage. The presence of
cleavage can be used to distinguish it from other minerals that often occurs in the same rocks.
Hornblende
USES OF HORNBLENDE
It is crushed and used for highway construction and as railroad ballast.
✓ It is cut for use as dimension stone.
✓ The highest quality pieces are cut, polished, and sold under the name “black granite”
✓ building facing
✓ floor tiles
✓ Countertops
✓ A generally black or dark green form of mica that is a constituent of crystalline rocks and consists of a
silicate of iron, magnesium, potassium, and aluminum.
✓ Abundant in metamorphic rocks (both regional and contact), in pegmatites, and also in granites and
other intrusive igneous rocks.
BIOTITE
Also known as “black mica”.
BIOTITE
a French physicist, mathematician, and astronomer who researched the mica minerals for their optical properties. biotite
Jean Baptiste Biot
- Occurs in platonic igneous rocks ranging from granites to gabbronorite to syenites. Large crystals may
form in pegmatites. - Can form phenocrysts in lava flows of dacitic or andesitic composition.
- Also common in metamorphic rocks where it is a frequent component of schists, gneisses and phyllites.
BIOTITE
WHAT MINERALS ARE IN BIOTITE?
Potassium, Iron, Magnesium, Aluminum, Silicate, Hydroxide, Fluoride
WHAT IS BIOTITE COMMONLY USED FOR?
- Commonly used to limit the age of rocks through potassium-argon escort or argon -argon escort.
- Also useful for evaluating the temperature histories of metamorphic rocks, because the division of iron
and magnesium between biotite and garnet is temperature sensitive.
dark colored mica. It is an aluminosilicate mineral that forms sheets or flakes.
BIOTITE
