Mineral Set 2 Questions Flashcards
(21 cards)
What are the elements involved in the solid solution between Actinolite and Tremolite?
Mg and Fe
Chemically, how does Hornblende differ from actinolite?
Hornblend has Na and Al in its composition.
How are amphiboles most readily distinguished from pyroxenes in hand samples?
Amphiboles have a cleavage of 56° and 124° while Pyroxenes have a ~90° cleavage.
Augite belongs to the Clinopyroxene series. A) What is the other main Pyroxene series and B) what are its end members?
Orthopyroxene. Its end members are Ferrosilite (Fe) and Enstatite (Mg).
What is Diopside and how does it relate chemically to Augite? How does it relate chemically to Wollastonite?
Augite = (Ca,Na)(Fe,Mg,Al)(Si,Al)2O6
*similar to diopside, but add Na,Fe,Al to the mix!
Diopside = CaMgSi2O6
Spodumene = LiAlSi2O6
Wollastonite = CaSiO3
Diopside-rich Pyroxene compositions are typically associated with what rock types? What minerals are found in these rocks?
Igneous and Metamorphic rocks (environments that support calcium rich/Magneisum rich minerals).
Plagioclase, Olivine, Biotite, garent, tremolite, actinolite, wollastonite, calcite and quartz.
Chemically, how is Spodumene distinct from other members of the pyroxene group?
Spodumene contains Lithium in it’s chemical composition: LiAlSi2O6.
What are the end members and compositions of Ca-free Olivine? Which is the higher temperature mineral?
Forsterite (Mg-rich) –> Higher temp.
Fayalite (Fe-rich)
What rock consists entirely of olivine?
Peridotite (aka Dunite)
How can Wollastonite be distinguished from Tremolite in hand sample?
Tremolite (amphibole) has a cleavage of 56° and 124°, while Wollastonite (Pyroxene) has a cleavage of 84°.
In what geological environment is Tourmaline most commonly found?
Felsic/Granitic Pegmatites.
What unusual elements are found in Tourmaline?
What properties distinguish Tourmaline from hornblende?
Li and B
Tourmaline has no cleavage, it has striated prism faces, and is harder than hornblende.
In hand sample, how is epidote distinguished from Olivine?
Olivine has no cleavage, epidote does. Epidote is more dark green than olivine, which is more pale.
In Kyanite, how many directions of cleavage are on the {100}? What is unsual about the hardness in the context of this cleavage?
One direction of cleavage appears of {100}.
Scratch hardness varies depending on the testing along or across cleavage.
What are common forms of garnet? What are the formulas? What are they shaped like?
Almandine, Grossular, Andradite
Almandine = Fe3Al2(SiO4)3 –> FEAL
Grossular = Ca3Al2(SiO4)3 –> CAAL
Andradite = Ca3Fe2(SiO4)3 –> CAFE
They typically have a habit of euhedral crystals that have the form of dodecahedral and/or trapezohedral faces.
What are the Polymorphs of Kyanite?
a) Which is high temp?
b) Which is low P, low-mod. T?
d) What variety is present in our mineral set?
Kyanite - Silimanite - Andelusite.
a) Silimanite = High T, High P
b) Andelusite = Low P, Low-Mod T.
c) Chiastolite. It is formed with the presence of carbonaceous material/graphite within the crystal structure.
Which members of the garnet group is found in Metamorphosed shales (Mica schists) and which are found in mantle rocks?
Almandine are found in Metamorphosed shales (Mica schists) and Pyrope is found in Mantle Rocks.
What kind of determinations are commonly carried out on zircon?
The use of Uranium/Lead for Radiometric Dating.
What use is Staurolite to metamorphic petrologists?
It is an index mineral in Metamorphic rocks. It can help determine the pressure and temperature that occurred during metamorphism, depending on what minerals it formed alongside.
How is Zircon related to cubic zirconia?
Cubic zirconia is synthetic and created using zirconia extracted from zircon.
How many directions of cleavage does topaz have?
One direction of perfect basal cleavage.
