Chapter 2.2

Definition of a Mineral  Naturally occurring- which means minerals are not a man-made substance.  Solid at normal temps on the Earth’s surface- What about ice? Glaciers?  Orderly Crystal Structure- Some crystals are microscopic, other are macroscopic.  Definite Chemical Composition- A recipe in specific proportions, such as H2O, SiO2, NaCl etc.  “Generally” Inorganic- Not from a living source. Sugar crystals are organic because they come from a plant. The rules are sometimes vague, because limestone (CaCO3) comes from living invertebrates, but is still considered a mineral.

Minerals Galena (PbS) Fluorite (CaF2) Halite, Rock Salt (NaCl) Muscovite Mica (KAl3Si3O10(OH)2

How do Minerals Form?  There are four major processes which are involved in the formation of minerals  Crystallization from magma- Magma cooling down to form igneous rocks.  Precipitation- Water that contains dissolved minerals evaporates, leaving minerals behind.  Pressure and Temperature- Example: Coal or graphite can change into a diamond.  Hydrothermal- Hot water mixed with minerals can form chemical reactions.

Mineral Formations Granite formed by Crystallization of Magma. Minerals present- Mica, Quartz, Feldspar Limestone precipitate from a Cavern Minerals present- Calcite (CaCO3) Garnet Schist formed by extreme heat and pressure Gold in a sample of Quartz formed by a hydrothermal solution

Minerals Groups  There are literally thousands of different minerals found all over the earth.  Is there an easier way to remember the minerals and their properties?  Yes, we can classify them into groups.  There are 6 different mineral groups based on their general compositions.

The Silicates  The Silicates are the most abundant minerals on the earth.  Silicates contain the elements silicon and oxygen.  Together they form covalent bonds to make a silicon-oxygen tetrahedron.  These are a few of the most common silicates: Quartz, Feldspar, Talc, and Mica.

The Silicates Silicates are not only abundant, but also very useful. Silicates are used not only to make glass and ceramics, but also to keep time in watches, to produce microchips for technology like your cell phones and computers. Silicates are some of the most widely used minerals on the planet.

The Carbonates  The second most abundant mineral group.  They contain the elements carbon, oxygen, and one or more other metallic elements.  Calcite and Dolomite are two common Carbonate minerals. They are found in rocks like Limestone and Marble.

The Carbonates The Mineral Calcite Stalactites and Stalagmites are made of Carbonates If you ever taken tums for an upset stomach you have consumed a carbonate mineral.

The Oxides  Oxides are minerals that contain oxygen and one or more other elements, which usually are metals.  Some examples of common oxide minerals include: Corundum (Al2O3), Hematite (Fe2O3), and Magnetite (Fe3O4)

The Oxides Rubies and Sapphires are made of Corundum Plain old rust is made of the mineral Hematite If you ever found a rock that is magnetic, chances are you found magnetite.

Sulfates and Sulfides  Sulfates and Sulfides are minerals that contain the element sulfur.  Sulfides like Gypsum form when mineral rich waters evaporate.  Sulfates like Galena and Pyrite form from hot hydrothermal solutions like hot springs.

Sulfates and Sulfides Pyrite, fools gold Galena Desert rose, GypsumOrdinary Gypsum

The Halides  The Halides are minerals that contain a halogen ion plus one or more other elements.  Halogens are elements that are in group 7A of the periodic table.  Some of the most common elements in group 7A are fluorine (F) and Chlorine (Cl).  Two common Halite minerals are halite (NaCl) and Fluorite (CaF2).  Both of these minerals form when mineral rich water evaporates.

The Halides Halite, Rock Salt Green Fluorite Purple Fluorite Dry Lake Bed in Death Valley Filled with Halite

Native Elements  Native Elements are a group of minerals that exist in relatively pure form.  Some common examples of native elements include gold (Au), silver (Ag), copper (Cu), sulfur (S), and carbon (C).  Graphite and diamond are both minerals that contain the element carbon, but their properties are very different.

Native Elements CopperGold Sulfur Diamond, a form of Carbon