Minerals and Bonding Mineral 1 Occurs naturally 2

Minerals and Bonding

Mineral 1. Occurs naturally 2. Is a solid 3. Has a definite chemical composition 4. Is inorganic Ex. Quartz, halite, mica, Gold, diamonds Non-minerals on earth Ex. Water, glass, pearls, coal 8 elements make up 98% of Earth’s crust

Non-minerals on earth l l l Native Mineral l l Almost always combined with other elements as chemical compounds. Top two or Two most abundant. Oxygen (O) & Silicon (Si) Mineral composed of a single element. Ex. Gold, copper, silver, sulfur, diamonds

How do atoms of different minerals stay together l Electric attraction l l l Ion l l Atoms in their normal state have an equal # of protons & electrons. Said to be “stable” An atom that gains or loses one or more electrons becoming either more positively or negatively charged Since opposite charges attract, ions of opposite charges may bond together to form a compound

Formation of Minerals • Most form in molten rock called “Magma” Type & Amount • The kinds of minerals that form depends in part on what elements are present and in what amount. • The rate at which the magma cools determines the size of the mineral Rate

Water-Based Minerals • • Other Info • • Crystalline • Minerals formed when water containing dissolved ions evaporates Ex. Halite (rock salt) Heat & pressure can also change substances into minerals All minerals are crystalline Made of atoms arranged in a regular pattern

Crystal • • • A regular geometric solid with smooth surfaces called crystal faces The angle at which crystals faces meet is always the same for each kind of mineral and can be used to help identify the mineral Although there are thousands of different kinds of minerals, only 6 basic crystal shapes occur

Crystallographic axes • • Descriptive shapes used to help identify each crystal system what are they? See figure 6 on page 7273

Silica Tetrahedron l l l In all Silicates l l 90% of the minerals in Earth’s crust are members of a mineral Family called Silicates These silicates are compounds of the elements Si & O plus 1 or more metallic minerals All silicates are made of four O atoms packed closely around a Si atom. Held together by covalent bonds between the Si and O atoms.

III. Identifying Minerals “More About Minerals!”

A. Rock-forming Minerals 1. The study of minerals and their properties is called MINERALOGY.

2. Examples: a. Quartz- hardest common mineral #7

b. Hornblende- very dense mineral

c. Feldspar- fleshly pink

d. Mica-dark, pearly color & flakes in sheets

e. Calcite- works as a natural cement &effervesces.

f. Olivine- olive green color

B. Mineral Identification 1. 2. Color- easy, but the least useful Luster- the way the mineral shines in the light. a. b. Metallic- shines like a polished metal Nonmetallic- no metal shine Ex. Glassy, pearly, oily, earthy, dull, waxy

3. Mineral tests: a. streak- color of a minerals powder, rubbing mineral on white tile b. cleavage- mineral tendency to spilt along flat surfaces. c. fracture- mineral breaks along surfaces that are NOT flat.

Fracture

Ex. Halite has 3 planes of cleavage.

d. Hardness- resistance to being scratched. 1. ) Moh’s Scale

d. Hardness- resistance to being scratched. 1. ) Moh’s Scale e. Specific gravity- ratio of mineral weight to weight of an equal volume of water. 1. ) How dense a mineral is compared to water.

f. Acid test- cold, weak HCl drop, look for a FIZZZZZ

5. Other special propertiesa. magnetic b. Fluorescence- glow under UV light 1. ) continue to glow after UV light is taken away = phosphorescent

5. Other special propertiesa. magnetic b. Fluorescence- glow under UV light 1. ) continue to glow after UV light is taken away = phosphorescent c. Radioactive d. Double refraction- bends light to form double image

Mineral Review 1. The study of minerals is termed? -MINERALOGY 2. What scale do we use for HARDNESS? -MOH’S 3. The least hard material can be scratched by what? - finger nail