Post on 18-Jan-2016
Objectives• Define a mineral
• Characterize how minerals are identified
• What are the different types of metals, non-metals, ores, and gems
Vocabularymineral
crystal
Silicates
LusterHardnessStreakCleavageGemOre
LusterHardnessStreak
CleavageGemOre
Mineral Characteristics• A mineral is
– naturally occurring • formed by natural processes
– Inorganic • Never living, never will be
– Solid– Specific chemical composition– Definite crystalline structure.
• Earth’s crust is composed of about 3000 minerals.
What is a mineral?
Mineral Characteristics
Definite Crystalline Structure
What is a mineral?
– Atoms in minerals are arranged in geometric patterns that are repeated again and again.
– A crystal is a solid in which the atoms are arranged in repeating patterns.
Cubic
Tetragonal
Hexagonal
Orthorhombic
Monoclinic
Triclinic
Minerals form in 2 ways
What is a mineral?
1. From Magma• Small crystals form from rapidly cooling magma.
• Large crystals form from slowly cooling magma.
Minerals form in 2 ways• 2. From Solution
What is a mineral?
– If a solution becomes supersaturated, or overfilled, with another substance, mineral crystals may begin to precipitate, or drop out of solution.
– When liquid evaporates the element remains and begins crystallize.
Mineral Groups• About 30 minerals are common in Earth’s crust.
What is a mineral?
• Called “rock-forming minerals” because they make up most of the crust.
• The vast majority of minerals are made up of the eight most common elements.
Mineral Groups
What is a mineral?
•Most minerals are formed from the eight most common elements in Earth’s crust.
Mineral Groups
1. Silicates
What is a mineral?
– Silicates contain silicon, oxygen, and one or more other elements.
– make up 96 percent of minerals in Earth’s crust.
– Most common: feldspar and quartz
Mineral Groups
2. Carbonates
What is a mineral?
– composed of one or more metallic elements with the carbonate compound CO3.
– the primary mineral found in rocks such as limestone and marble.
Mineral Groups
3. Oxides
What is a mineral?
– compounds of oxygen and a metal.
– Hematite (Fe2O3) and magnetite (Fe3O4) are common iron oxides and good sources of iron.
Mineral Identification• Geologists use several simple tests to identify
minerals.
Identifying Minerals
• Tests are based upon a mineral’s physical and chemical properties.
Six Mineral Identification Tests
Identifying Minerals
1. Color is one of the least reliable clues to a mineral’s identity
– trace elements or compounds within a mineral can change its color.
2. Luster is the way that a mineral reflects light
– is described as either metallic or nonmetallic.
3. Texture describes how a mineral feels.
– Texture can be described as smooth, rough, ragged, greasy, soapy, or glassy.
Six Mineral Identification Tests
Identifying Minerals
4. Streak is the color of the fine powder of a mineral obtained by scratching or rubbing against a hard white surface.
• Sometimes, a mineral’s streak does not match the mineral’s external color
5. Hardness is a measure of how easily a mineral can be scratched.
– one of the most useful and reliable tests for identifying minerals.
Six Mineral Identification Tests
6. Cleavage & Fracture - Minerals break along planes where atomic bonding is weak.
– Cleavage some minerals split easily and evenly along one or more flat planes.
– Fracture is the ability of minerals to break with arclike, rough, or jagged edges.
Special Properties• Special properties of minerals also can be used
for identification purposes.
Identifying Minerals
– A type of calcite called Iceland spar causes light to be bent in two directions, a process known as double refraction, when it passes through the mineral.
– Calcite (CaCO3) fizzes when it comes into contact with hydrochloric acid (HCl).
– Magnetite, an iron ore, is naturally magnetic.
– The mineral sphalerite produces a distinctive rotten-egg odor when it is rubbed vigorously across a streak plate.
Mineral Uses
Ores
Identifying Minerals
– An ore is a mineral that contains a useful substance that can be mined at a profit.
- If the cost of separating waste material from ore becomes higher than the value of the ore itself, then the mineral is no longer considered to be an ore.
– The classification of a mineral as an ore may also change if the supply of or demand for that mineral changes.
Gems• Gems are valuable minerals that are prized for
their rarity and beauty.
Identifying Minerals
• Gems such as rubies, emeralds, and diamonds are cut, polished, and used for jewelry.
• In some cases, the presence of trace elements can make one variety of a mineral more colorful and thus more prized than other varieties of the same mineral.