Activity: Minerals Part 1

1. Each of the following pairs of minerals are polymorphs. What is the formula of the second mineral? (5 pts)

2. Classify the following minerals as either carbonates, sulfides, sulfates, salts, oxides, or silicates. (7 pts)

Rhodochrosite,

MnCO3

Sylvite, KCl

Pyrite, FeS2

Barite, BaSO4

Diopside,

CaMgSi2O6

Stishovite,

SiO2

Hematite, Fe2O3

Determine the type of polymerization for each of the following silicate minerals. I’ve done the first one for you as an example (20 pts)

Mineral	Polymerization
Diopside, CaMgSi2O6	single chain

Talc, Mg3Si4O10(OH)2

Albite, Na[AlSi3]O8

Quartz, SiO2

Forsterite, Mg2SiO4

Riebeckite, Na2(Fe²⁺3Fe³⁺)Si8O22(OH)2

Jadeite, NaAlSi2O6

Lepidolite, LiAl2[AlSi3]O10(OH)2

Pyrope, Al2Mg3Si3O12

Magnesiohornblende, Ca2(Mg4Al)[AlSi7]O22(OH)2

4. Sketch the silicon tetrahedron below and give its formula and charge (10 pts)

Minerals always incorporate “impurities” into their structures when they grow. Although any element can be found in nearly every mineral, relatively abundant impurities occur when its cation has the same charge and similar size compared to the expected cation on a given site. For example, because Fe²⁺ and Mg²⁺ have the same charge and are nearly the same size, Fe²⁺ is almost always found to some degree on the octahedral sites in olivine, Mg2SiO4. On the other hand, talc contains vanishingly small amounts of K because the K⁺ cation is both much too large and has the wrong charge for any of the sites in olivine.

Use the periodic table to predict whether the following elements will occur as significant impurities in each of the following minerals (20 pts)

Element	Mineral	Significant substitution? (Y/N)

Rb	K-spar, K[AlSi3]O8

Cs	K-spar, K[AlSi3]O8

Sr	Plagioclase, (Na,Ca)[Al,Si]4O8

Al	Anhydrite, CaSO4

Al	Diopside, CaMgSi2O6

Rb	Diopside, CaMgSi2O6

Ra	Diopside, CaMgSi2O6

Mg	Calcite, CaCO3

Al	Calcite, CaCO3

Mn	Calcite, CaCO3

Write the formulas for the following minerals, which are common minerals you will often encounter near the surface of Earth, especially in Florida. You will need to memorize these formulas for the exams. (8 pts)

Quartz

Calcite/aragonite

Dolomite

Gypsum