1. Properties
Uses
Identification

2. Definition
1. Naturally Occurring
2. Inorganic solid
3. Chemical Composition (i.e. NaCl, Au)
4. Physical Properties
5. Crystalline Structure (3‐D arrangement)

3. Property 1: Color
 The least reliable property of minerals
 Some minerals have more than one color, and many
minerals may have the same color
 Clarity: transparent, translucent, opaque

4. Property 2: Crystal Form
 Crystal geometry: cube, pyramid, tetrahedron, etc.
 External property
 Perfect form = RARE

5. Property 3: Luster
 Describes light reflection from mineral surface
 Metallic (M): silver, gold, copper, steel
 Nonmetallic (NM): not metallic
 Vitreous – glass
 Waxy – candle
 Pearly
 Satiny
 Earthy – dull, no reflection
 Greasy – oily
 Porcelaneous – translucent white

6. Property 4: Hardness
 Mineralogist Friedrich Mohs
(1773‐1839)
 Resistance to scratching
 Hard: scratch glass (>5.5)
 Soft: cannot scratch glass (<5.5)
 Streak plate = 6.5

7. Property 5: Streak
 Streak: color of a mineral after it
is ground to a fine powder
 Use a streak plate
 CAUTION: streak plate has
hardness = 6.5 (white powder)
 If >6.5, crush with hammer

8. Property 6, 7: Cleavage/Fracture
 Cleavage: minerals break (cleave) along surfaces
 Weak chemical bonds
 Cleavage direction: parallel surface of break
 Fracture: break not along cleavage planes
 Not flat, not parallel sets

9. Other Important Properties
 Reaction to HCl (calcite, powdered dolomite)
 Magnetism: magnetite