Minerals

How Some Minerals Form

• mineral: always a solid material with particles arranged in a repeating pattern– the pattern is called a crystal– almost all minerals are made from material that was

never alive– true minerals only form in nature

• diamonds form in Earth’s mantle– high heat and pressure change carbon into

hard, sparkling crystals called diamonds– diamonds have many uses

• some are cut and shaped to make jewelry• most are used on cutting tools such as drills and

saws

• calcite can form near Earth’s surface• calcite can form in the ocean when

calcium, oxygen, and carbon combine in sea water– some ocean animals form calcite shells or

other body parts

• calcite also forms as water evaporates in limestone caves

• galena crystals form when hot, mineral rich water moves slowly through cracks in Earth’s crust, mixing with other minerals before it cools and evaporates

Some Mineral Properties

• streak: color of the powder left behind when you rub a mineral against a white tile called a streak plate– usually the streak is the same color as the

mineral– chalcopyrite looks shiny black but streaks

gold

• luster: the way the surface of a mineral reflects light– some minerals look shiny - metallic luster– some minerals look dull/dark - nonmetallic

luster– sparkling appearance of a diamond is known

as a brilliant luster

• hardness: a mineral’s ability to resist being scratched– Moh’s hardness scale lists minerals that have

hardness from 1 to 10– a mineral with a higher number can scratch a

mineral with a lower number

How We Use Minerals

• some minerals can be used in the same form as they have in nature– silver and copper can be used to make

musical instruments, electric wire, jewelry– gypsum can be used to make plaster and

wallboard– graphite can be used in pencils– halite (table salt) can be use to flavor and

preserve food

• silver is a soft metal– hardness of 2– mixed with other metals to make jewelry or musical

instruments

• hematite is made of iron and oxygen– hardness of 5 - 6.5– important source of the iron used to make steel

• steel beams used to make tall buildings strong

• diamond is the hardest natural substance found on Earth– hardness of 10– used to make jewelry– diamonds not good enough for jewelry used on

drills that dig deep into Earth’s crust

• some minerals are not useful in their natural form– need to be refined– cuprite is made of copper and oxygen

• when cuprite is refined the copper is used in pennies, pots, pans, and water pipes

Summary

• some minerals form in Earth’s mantle and others form at or near the Earth’s surface

• minerals can be identified by their properties– streak, hardness, and luster

• minerals have many uses