Mineralogy and Petrology Flashcards

The silica tetrahedron (SiO₄⁴⁻) in olivine group minerals is arranged as:

Answer: Isolated tetrahedra with no shared oxygens

Olivine is a nesosilicate (island silicate) where each SiO₄ tetrahedron shares no oxygens with neighboring tetrahedra.

Which sedimentary rock, upon contact metamorphism, typically recrystallizes to form marble?

Answer: Limestone or dolostone

Limestone and dolostone are carbonate rocks that recrystallize to marble under heat and pressure, coarsening the calcite or dolomite grains.

In igneous petrology, the term 'cumulate' refers to rocks formed by:

Answer: Crystal settling or accumulation from a magma chamber

Cumulate rocks form when early-crystallizing minerals sink or float in a magma chamber and accumulate into distinct layers.

Which mineral group includes muscovite, biotite, and phlogopite?

Answer: Micas

Muscovite, biotite, and phlogopite are all sheet silicates belonging to the mica group, characterized by perfect basal cleavage.

A granodiorite differs from a true granite primarily in having:

Answer: More plagioclase than alkali feldspar

Granodiorite contains more plagioclase than alkali feldspar (P/(A+P) ratio 65–90%), while granite has more alkali feldspar.

The mineral magnetite (Fe₃O₄) belongs to which mineral class?

Answer: Oxides

Magnetite is an iron oxide mineral (spinel group) classified in the oxide mineral class, strongly magnetic and commonly found in mafic igneous rocks.

Pressure solution in metamorphic rocks occurs when:

Answer: Minerals dissolve preferentially at grain-to-grain stress concentrations

Pressure solution is a deformation mechanism where minerals dissolve at high-stress contact points and may reprecipitate elsewhere, leading to grain compaction and stylolites.