Mineral Identification Aim: How do we identify minerals? Chapter 3: section 2

 A physical property is any characteristic of a material that you can observe without changing the identity of the material.  Example: How would you distinguish pyrite (fool’s gold) from gold?

 Color  Appearance  Example:  Pyrite and fool’s gold are both gold in color.  Gold is worth a lot of money.  Pyrite has little value.

 Hardness is the measure of how easily a mineral can be scratched.  The mineral talc is so soft you can scratch it with your fingernail. This is the softest mineral.  Diamonds are the hardest mineral.  Example: gold – hardness pyrite – hardness (***Do not confuse hardness with how a mineral can break***)

 Friedrich Mohs developed a list of common minerals to compare their hardnesses.  This list is called Mohs scale of hardness.

 Some minerals have a hardness range rather than a single hardness value. This is because atoms are arranged differently in different directions in their crystal structures.

 A way a mineral reflects light is known as luster.  Luster may be metallic or nonmetallic.  Metallic – shines like a metal  Nonmetallic – glassy, dull, pearly, silky

 Minerals can be compared by comparing the weights of equal-sized samples.  The specific gravity of a mineral is the ratio of its weight compared with the weight of an equal volume of water.  Example: Gold is 19 times heavier than water. Pyrite is 5 times heavier then water.  The tern heft describes how heavy a mineral sample feels.

 When a mineral is rubbed across a piece of unglazed porcelain tile, a streak of powdered mineral is left behind.  Streak is the color of a mineral when it is in a powdered form.  The streak test only works for minerals that are softer than the streak plate.  Example: Gold – yellow streak Pyrite – greenish-black/ brownish-black streak

 Minerals that break along smooth, flat surfaces have cleavage.  Cleavage like hardness is determined partly by the arrangement of a minerals atoms.  Minerals that break with uneven, rough, or jagged surfaces have fracture.

 Some minerals may have unique properties.  Magnetite – attracted to magnets