Minerals can only form in rocks of appropriate bulk composition. Therefore, mine

Question

Minerals can only form in rocks of appropriate bulk composition. Therefore, minerals are indicative of the bulk composition of a rock. For the different feldspar and phyllosilicate minerals, as well as the ino-, neso-, soro-, cyclosilicatcs. place the minerals in the correct igneous rock type. This is an excellent review and will come in handy in petrology class! Silicic (e.g. granites, rhyolites) Mafic (e.g. basalts, gabbros) Ultramafic (e.g. peridotites, dunites) Pegmatites Si-undersaturatcd - alkalic

Explanation / Answer

Felsic/silicic

65% silica; K-feldspar, quartz, Na-rich plagioclase, muscovite, + minor mafic silicates (Biotite + amphibole);

Mafic

45 - 55% silica; Ca-rich plagioclase, pyroxene + minor olivine; dark + dense; most common rocks of oceanic crust.

Ultramafic

Pegmatite

These are extreme igneous rocks that form during the final stage of a magma’s crystallization. They are extreme because they contain exceptionally large crystals and they sometimes contain minerals that are rarely found in other types of rocks.

Most pegmatites are granites with or without exotic minerals, but mafic pegmatites (gabbro, diorite) are known as well. Silica under saturated (without quartz) magmatic rocks may be also pegmatitic.

Si-under saturated Alkali (Foidolites)

Mineral content:

Essential minerals: clinopyroxene (Ti-augite, aegirinaugite, aegirine), nefeline

Accessory minerals: olivine, flogopite, leucite, zircon, apatite, magnetite and/or ilmenite, carbonate minerals, garnet (melanite)

Secondary minerals: sericite, epidote, chlorite

Rock types: Jacopirangite: pyroxene-rich variety of ijolite

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