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Hornblende alters easily to chlorite, biotite, or other mafic minerals. [14] A rare variety of hornblende contains less than 5% of iron oxide, is gray to white in color, and is named edenite from its locality in Edenville, Orange County, New York. Oxyhornblende is a variety in which most of the iron has been oxidized to the ferric state, Fe 3 ...
The series is divided into two branches, the continuous (felsic minerals: feldspars) and the discontinuous (mafic minerals).The minerals at the top of the illustration (given aside) are first to crystallize and so the temperature gradient can be read to be from high to low with the high-temperature minerals being on the top and the low-temperature ones on the bottom.
Diorite. Diorite (/ ˈdaɪ.əraɪt / DY-ə-ryte) [1][2] is an intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is intermediate in composition between low-silica (mafic) gabbro and high-silica (felsic) granite.
In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz. [1] It is contrasted with mafic rocks, which are richer in magnesium and iron. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium ...
The black crystal is garnet, the pink-orange-yellow colored strands are muscovite mica, and the brown crystals are biotite mica. The grey and white crystals are quartz and (limited) feldspar. Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture.
These rocks contain also iron oxides (usually titaniferous), apatite, sometimes sphene, augite, and olivine. The hornblende and biotite are brown or greenish-brown, and as a rule their crystals even when small are very perfect and give the thin section views an easily recognizable character. Green hornblende occurs in some of these rocks.
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium -rich varieties of plagioclase ...
The Farmington Gabbro is postmetamorphic medium to coarse grained plutonic rock next to metagabbros. [2] The unit is surrounded by Proterozoic to early Paleozoic metamorphosed rock. [1] The major and trace elements of the pluton matches the composition of calc-alkaline basaltic magma. [2] The minerals present are plagioclase, hornblende ...