Minerals Charity I. Mulig

Definition A Mineral is a naturally occurring Inorganic Solid with a definite chemical composition and a crystalline structure.

How do minerals form? 1.Crystallization from magma 2.Precipitation 3.Pressure and Temperature 4.Hydrothermal solutions

Properties of Minerals

Crystalline Structure The orderly arrangement of ions, molecules, or atoms, in any mineral determines the shape of its crystals. Six Basic Crystal Shapes Cubic Orthorhom bic Tetragonal

Crystalline Structure The orderly arrangement of ions, molecules, or atoms, in any mineral determines the shape of its crystals. Six Basic Crystal Shapes Triclinic Hexagonal Monoclinic

ColorColor Color is the most easily observed, but least reliable property of a mineral for identification. This is because the color of many minerals varies with the kind of impurities in the mineral.

Luster Types of Luster Metallic Shiny Glassy Earthy is the way in which a mineral shines in the light.

Streak Streak is the color of the powder left on a streak plate when a mineral is rubbed on it. Streak is much more reliable than color because, although the color of a mineral changes, its streak does not.

Cleavage Cleavage is the tendency of a mineral to split in a particular direction.

“Sheety” Cleavage

Fracture Fracture is the tendency of a mineral to break in directions other than along crystal faces or cleavage surfaces.

Conchoidal or shell-like fracture Fibrous facture

is the resistance of a mineral to being scratched. The Mohs Hardness Scale is one of the most effective tool for identifying minerals.

Examples

Density Sometimes equated to specific gravity Density is a property of all matter that is the ratio of an object’s mass to its volume while specific gravity is the ratio of an objects density to the density of water.

Mineral Groups

Silicates Largest group of minerals. Silicon and oxygen combine to form a structure called the silicon-oxygen tetrahedron. Silicates are combinations of metal ions and the silicon-oxygen tetrahedron. Examples: Feldspars, Micas, Amphiboles, Pyroxenes, Olivine, Garnets, Kaolin

Oxygen atom Silicon atom

Carbonates Made up of ions (usually metallic elements) joined with the carbonate ion (CO 3 ) 2−. Examples: Calcite, Dolomite, Malachite, Azurite, Onix, Alabaster, and Chalk are all examples

Oxides Minerals that contain oxygen and one or more other elements, which are usually metals Form many of the ores from which valuable metals are extracted. Carry the best record of changes of the earth’s magnetic field. Examples: Hematite, magnetite, chromite, spinel, ilmenite, rutile and ice.

Sulfates and Sulfides SulfatesSulfides contain the sulfate anion, SO 4 2 commonly form in evaporitic settings, in hydrothermal vents and during oxidation of sulfide minerals Important as metal ores Examples: anhydrite(calcium sulfate), celestine (strontium sulfate), barite (barium sulfate), gypsum (hydrated calcium sulfate), chromate, molybdate, selenate, sulfite, tellurate, and tungstate minerals. Examples: pyrite (iron sulfide – commonly known as fools' gold), chalcopyrite (copper iron sulfide),pentlandite(nickel iron sulfide), galena (lead sulfide), the selenides, the tellurides, the arsenides, the antimonides, the bismuthinides, and the sulfosalts (sulfur and a second anion such as arsenic).

Halides Minerals that form the natural salts Usually form in evaporitic settings Minerals that contain a halogen ion plus one or more other elements Examples: fluoridefluoride, chloride, bromide and iodide minerals.chloridebromideiodide

Native Minerals Also known as native elements Minerals that exist in relatively pure form Include native metals, intermetallic elements and alloys Examples: Gold, silver, copper, antimony, bismuth, graphite, sulfur, phosphides, silicides, nitrides, and carbides.

Trivia There are about 4000 different minerals in our planet. Thirty of which are common and are called rock-forming minerals. More than 90% of all of the minerals in the Earth’s Crust are made up of compounds containing Silicon and Oxygen, the two most abundant elements on Earth. High silica content rocks are light colored while lower (by about 25%) silica content rocks have darker colors.

Trivia Different types of minerals crystallize at different temperatures (as shown in the Bowen’s Reaction Series).

Additional Resources Tarbuck Ph Express Links on Minerals dex.html Gems and Minerals Photo Gallery Glossary of Terms (Gems) Minerals Database Helpful Tables (on Minerals) List of Crystal Structure Movies