Properties of Minerals

Target #12- I can state how minerals are classified

• Minerals are classified by their properties– Some are easy to study, other require equipment– Determined by the chemical composition and

crystalline structure– Properties

• Color• Streak• Luster• Cleavage & Fracture• Hardness• Crystal Shape• Density

Target #13- I can explain why color is an unreliable clue to the identify of a mineral

• Color– Easy to observe with the

naked eye• Example

– Quartz» Pure: colorless» Amethyst: purple (due to the

presence of iron and manganese)

– Sapphire» Medium to dark blue in color» Caused by the presence of

iron and titanium

– Not generally reliable for identifying a particular mineral• Weathered surfaces may hid

the color of minerals

Target #14- I can state how you would determine the streak of an unidentified

mineral• Streak

– The color of the mineral in a powdered form

– Easiest way to observe is to rub the mineral against a piece of unglazed tile

– Different minerals produce different streaks• Example

– Pyrite gold in color, streaks black

– Minerals harder than the tile will not streak

Target #15- I can describe two types of luster

• Luster– Light that is reflected on

a mineral’s surface• Either metallic, can reflect

light, or non-metallic

– Non-metallic luster is broken down further• Waxy luster

– Look like candle wax

• Glassy luster– Look like glass

• Pearly luster– Look like pearls

• Dull luster– Lacks any shiny

appearance

Target #16- I can contrast cleavage and fracture

• Cleavage & Fracture– Cleavage: the tendency of a

mineral to split along specific planes of weakness to form smooth flat surfaces• Weaknesses tend to run

parallel• Example

– Mica split into sheets

– Fracture: minerals can break unevenly into pieces that have curved or irregular surfaces• Described according to their

appearance

Target #17- I can summarize how you would determine the hardness of an unidentified

mineral sample

• Hardness– The measure of the ability of a mineral to resist

scratching– Can be determined by using the Mohs hardness

scale• Scratch an unknown mineral to those found on the

hardness scale

– To test for hardness, you must determine the hardest mineral on the scale that the unknown mineral can scratch• If you scratch the unknown with the known, and vice

versa, and they do not mark each other, then they are the same hardness

Target #18- I can state how environmental conditions impact mineral formation

• Crystal Shape– Forms into one of six basic

shapes– Can become more complex

as a result of environmental conditions during crystal growth• Example

– Temperature– Pressure

Target #19- I can explain the apparent weight differences observed between minerals of the same

size

• Density– The ratio of the mass of

a substance (how much “stuff” is in it) to the volume of the substance (how much space there is)

– The more tightly packed the atoms, the more dense a substance is

– Explains the apparent differences in weight between minerals of the same size