What is a Mineral?

WHAT IS A MINERAL?Earth ScienceChapter 4Section 1

Mineral Characteristics Mineral Naturally occurring

Inorganic Solid Specific chemical

composition Definite crystalline

structure

Rock Forming Minerals 3000 minerals occur in Earth’s crust 8-10 refered to rock forming minerals

Make up most of the rocks

Minerals from Magma Magma less dense than

surrounding rocks Rises

As cools, crystals form Elements in magma determine

the mineral formed Large crystals

Cool slowly, atoms have time to arrange in large crystals

Small crystals Rapidly cooling magma

Minerals from Solution Minerals dissolved in water

Salts Saturated

Water can’t hold any more of the substance Supersaturated - Precipitates

Solution becomes overfilled Conditions right for minerals to form Individual atoms bond together and mineral

crystals form into solids from the solution

Minerals form Solutions Evaporates

Minerals crystallize when the solution evaporates

Crystal Form Distinct crystal shape

Easily recognizable Halite- cubes Quartz - double pointed ends

Perfect crystals are not the norm Crystallization should not be used as only

form of identification

Luster

Metallic luster Shiny surfaces

that reflect a lot of light

Nonmetallic luster Do not shine

Dull, pearly, waxy, silky or earthy

Metallic Luster Non Metallic Luster

Hardness Hardness is the

measure of how easily a mineral can be scratched.

Most useful and reliable of all tests

Mohs Hardness Scale used to compare minerals

Cleavage and Fracture

A mineral that splits easily alone one or more flat planes

Minerals that bread with rough jagged edges

Cleavage Fracture

Conchoidal fracture

Streak The powder left

on a ceramic plate when a mineral is scratched along it.

Does not always match the color of the mineral.

Color Most noticeable

characteristic Least reliable Sometimes

caused by trace elements or compounds within the mineral

Special Properties Magnetism Striations Double refraction

Light is split into two rays Effervescence

Does if fizz? Fluorescence

Shine in ultraviolet light

Texture How the mineral feels to the touch Subjective Used with a combination of tests

Specific Gravity Ratio of the weight of the mineral with

the weight of an equal volume of water. Specific gravity of minerals can be

roughly relatively tested using heft.