Notes: MINERALS! (4.1- 4.2)

Characteristics that make a Mineral. . . Naturally made Solid Inorganic (never living or from living things) Unchanging chemical composition/formula Crystal structure

General Facts about Minerals Almost 4000 have been identified! A few are “native elements” -- made of only one element that exists by itself, (such as gold or copper) and also rock-forming elements. Most are compounds Sometimes, compounds are only minerals when they’re in a certain phase of matter (ice, diamonds) but not in others. A gem is a valuable mineral that is prized for it’s appearance.

COMMON CHEMICAL GROUPS OF MINERALS: “Silicates” (--SiO4) – Are pyramid-shaped groups, and can form chains and sheets very easily. Usually has a “glassy” sheen or specks when seen in rocks. What type of bonding?

(3)“Oxides” and “Hydroxides” (--03 / --OH ) (2) “Carbonates” (--CO3) Can take on many appearances, but appear mostly powdery/chalky when broken down. These fizz with the acid test. (3)“Oxides” and “Hydroxides” (--03 / --OH ) These contain metals combined with other elements. They can be very swirly and colorful looking.

Since there are 4000+ known minerals, there are tests in place to identify them: Breakage: Cleavage vs. Fracture Density (specific gravity) Special properties --reaction to acid --fluorescence --salty taste --magnetism Hardness Crystal shape (form) Luster Color Streak

Mineral Hardness Ability to scratch another mineral To use the scale for example, a fingernail can only scratch what’s under it (Gypsum and Talc). What ever is above you on the scale can scratch you. What ever is below, you can scratch.

Example: What minerals can scratch QUARTZ? What’s the hardest mineral? What’s the softest? What tools can scratch CALCITE?

Crystal Shape (Form) External shape due to internal arrangement of the atoms (LATTICE). . . The longer the cooling time, the larger the crystals, because atoms have “time” to organize. All minerals have crystals, even if it doesn’t look like it!

Crystal Formation. . . Minerals need to be dissolved in a solution There needs to be a source of heat They need to be left undisturbed for a long time They need room for atoms to arrange in a lattice structure

Luster Describes how light reflects off the surface Main categories are “metallic” and “non-metallic” Non-metallic includes “dull,” “vitreous (glassy)”, “ waxy,” “pearly,” and others

Why????? . . . (What kind of bonding?) Metallic elements can also be malleable (able to be pounded into different shapes) Metallic elements can also be ductile (able to be pulled into wires)

Color & Streak Overall color results from ability to absorb some wavelengths of light, and reflect others Other color differences vary due to chemical differences or impurities (atoms mixed inside the main elements)

….Streak Color of the powder when rubbed on a “streak plate” (unglazed porcelain) Some paint is based on powdered minerals (streaks). Most minerals just have a white streak

Breakage: Cleavage vs. fracture Some minerals split along flat surfaces when struck hard or pried apart--this is called mineral cleavage Other minerals break unevenly along rough or curved surfaces--this is called fracture A few minerals have both cleavage and fracture

Density (Specific Gravity) All minerals have density (mass / volume), but some are very dense. Examples include Galena, Magnetite, and Gold Specific Gravity is the density of the mineral compared with density of water

Special Characteristics-- the “Acid Test” Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas)

Special Characteristics-- Fluorescence Some minerals will glow when placed under ultraviolet rays Franklin and Ogdensburg, NJ are famous for their fluorescent minerals

Special Characteristics-- Salty Taste DO NOT TASTE MOST MINERALS! Halite is the exception--it will taste salty

Special Characteristics-- Magnetism Many iron minerals will produce an invisible magnetic force field “Lodestone” (Magnetite) was used by Vikings more than 1,000 years ago as compasses

ORE A mineral-bearing rock who’s mineral is mined, purified, and sold for profit. Examples: Bauxite is an ore of Aluminum