Understanding Mineral Groups: Composition and Classification of Earth’s Crust

1. Mineral Groups Nearly 4000 minerals have been discovered and named; however, no more than a few dozen are abundant. These few dozen makes up most of the rocks that comprise Earth’s crust. This is why we call them the rock-forming minerals. Minerals that form the rocks within Earth’s crust belong to seven (7) main mineral groups, which include: 1) Silicates 2) Carbonates 3) Sulfates 4) Oxides 5) Halides Reference: Tarbuck and Lutgens Pages 44 - 55 6) Sulfides 7) Native Elements

2. Do You Remember? • Do you remember the eight elements that make up more than 98 % of Earth’s crust (i.e. continental crust)? List them. • Which two elements are most abundant in Earth’s crust? Oxygen and Silicon. • Both comprise nearly three-fourths of Earth’s continental crust. Both elements combine to form the framework of the most common mineral group (i.e. the silicates). • The framework is called the silicon-oxygen tetrahedron.

4. Mineral groups that end with “ate” and have an oxygen group in its chemical formula are one of the following; Silicates = Si + Oxygen Sulfates = S + Oxygen Carbonates = C + Oxygen Hints To Classify Mineral Groups Olivine (Mg,Fe)2SiO4 Barite BaSO4 Calcite CaCO3

5. Mineral groups that end with “ide” and have a metal (e.g., Na, K) in its chemical formula are one of the following; Oxides = Metal + O Sulfides = Metal + S Halides = Metal + Cl, Br, F Hints to Classify Mineral Groups Hematite Fe2O3 Pyrite FeS2 Fluorite CaF2

6. 1) Silicates Mineral Groups • A mineral group that has silicon and oxygen as part . of their atomic structure. • Comprise more than 96% of the crust (most common mineral group). Rock forming silicates are divided into two groups: • Sialic Silicates (Aluminosilicates) • Rich in silicon and aluminum. • Comprise about 85% of the silicates in the crust. • Mineral are light in color. Examples include: Quartz Mica (Muscovite) Feldspar

7. 1) Silicates (Continued) Mineral Groups • Simatic Silicates • Rich in silicon and magnesium. • Comprise less than 15% of the silicates in the crust. • Minerals are dark in colour. Examples include: Olivine Pyroxene Amphibole

8. 2) 3) Carbonates Sulfates • compounds consisting of an atomic structure of one sulfur and four oxygen (SO4). Mineral Groups • compounds consisting of an atomic structure of one carbon and three oxygen (CO3). • most common carbonate mineral is calcite (Ca CO3), which makes up the chemcial sedimentary rock called limestone as well as the metamorphic rock called marble. • the rock gypsum is an example of a sulfate and it also takes on the mineral name. (CaSO4• 2H2O) • The mineral barite (BaSO4) is mined and used in drilling mud.

9. 4) 5) Oxides Halides • compounds consisting of an atomic structure of chlorine or fluorine with sodium, potassium, or calcium. Mineral Groups • compounds consisting of an atomic structure of oxygen combined with one or more metals. • most common oxides are those of iron (Fe2O3) and aluminum (Al2O3); referred to as the Ore Minerals. As an example, the mineral hematite is Fe2O3 • Halite (NaCl) is the most common halide. It is often referred to as table salt.

10. 6) 7) Sulfides Native Minerals • elements that occur uncombined in nature. • commonly called native elements. Mineral Groups • compounds consisting of an atomic structure of one or more metals combined with sulfur. • examples of minerals include: pyrite (FeS2), galena (PbS), and sphalerite (ZnS). • examples include: gold (Au), silver (Ag), copper (Cu), and sulfur (S).

11. NOTE • Note that an ore mineral is any mineral that has enough of a particular element in it to be mined at a profit. $

12. Sample Problem Which is an example of a halide? (A) barite (BaSO4) (B) calcite (CaCO3) (C) fluorite (CaF2) (D) hematite (Fe2O3)