Minerals

What is a Mineral? Naturally-formed solid substance with a crystal structure Pyromorphite

What do all minerals have in common? Are formed by natural processes. Are NOT alive and NEVER were alive Have a definite volume and shape Are elements or compounds with a unique chemical makeup Are made up of particles that are arranged in a pattern that is repeated over and over (called a CRYSTAL)

Groups of Minerals Minerals are grouped by the elements they are made of. Beryl (Emerald) Calcite Amethyst

Contain oxygen & silica The most abundant group of minerals Mineral Group Characteristics Examples Silicates Contain oxygen & silica The most abundant group of minerals Quartz, mica MICA Quartz

Mineral Group Characteristics Examples Oxides Metallic ion and oxygen Hematite (Fe2)O3

Mineral Group Characteristics Examples Sulfides Sulfur and a metallic ion Galena (PbS)

Metallic ion, Sulfur & oxygen Barite (BaSO4) Mineral Group Characteristics Examples Sulfates Metallic ion, Sulfur & oxygen Barite (BaSO4) Barite BaSo4 Barite on Calcite BaSo4 / CaCO3

Halite (rock salt) (NaCl) Fluorite (CaF2) Mineral Group Characteristics Examples Halides Include a halogen ion (group 17) and a metal from the left side of the periodic table Halite (rock salt) (NaCl) Fluorite (CaF2) Halite Fluorite

Carbon & oxygen and a positive ion, such as calcium Calcite (CaCO3) Mineral Group Characteristics Examples Carbonates Carbon & oxygen and a positive ion, such as calcium Calcite (CaCO3) Calcite with Duftite inclusions

Mineral Group Characteristics Examples Native Elements Single elements Gold (Au), Diamond (C), Silver (Ag)

How do minerals form? 1) Cooling of magma (hot, liquid rock and minerals inside the earth (from the mantle)) Fast Cooling = No Crystals (mineraloids) Medium Cooling = small crystals Slow Cooling = large crystals

How do minerals form? 2) Elements dissolved in liquids (usually water)

Physical Properties of Minerals (can be used to identify the mineral) Color Can be misleading Can vary with the type of impurities

Physical Properties of Minerals (can be used to identify the mineral) Luster Surface reflection metallic = shiny like metal non-metallic = dull, non-shiny surface Pyrite has a metallic luster Quartz has a non-metallic luster

Physical Properties of Minerals (can be used to identify the mineral) Streak The color of the powdered form of the mineral The color of the streak can be different than the mineral Minerals must be softer than the streak plate

Streak…can help identify quartz BUT... http://www.childrensmuseum.org/geomysteries/cube/b3.html

Physical Properties of Minerals (can be used to identify the mineral) Hardness How easily a mineral scratches materials Mohs Hardness Scale Scale from 1 (softest) to 10 (hardest) Test by seeing if the mineral can scratch different objects (like human fingernail, copper, penny, glass, steel file)

Find out more… “Electronic” Hardness Test http://www.childrensmuseum.org/geomysteries/cube/b2.html

Physical Properties of Minerals (can be used to identify the mineral) Cleavage & Fracture The way the mineral breaks Cleavage—minerals break along smooth, flat surfaces and every fragment has the same general shape Fracture—minerals that break at random with rough or jagged edges

Cleavage or Fracture? 1. 4. 3. 2.

Physical Properties of Minerals (can be used to identify the mineral) Other Properties Specific gravity (*excellent clue to mineral’s identity) Attraction to magnets Bending of light Reaction with hydrochloric acid Smell & taste http://www.childrensmuseum.org/geomysteries/cube/b4.html