N. Lindsley-Griffin, 1999

Quartz

• Even when the crystals are different sizes, angles between equivalent faces are the same

• For different minerals, angles are different.

3 3

1 12 2

4 4

Crystal Interfacial AnglesCrystal Interfacial Angles

N.Lindsley-Griffin, 1999

HabitHabitHabit - distinctive shape of the way the mineralcommonly (habitually) appears

Concentric shells -- malachite

N. Lindsley-Griffin, 1998

HabitHabit

Crystal shape and Habit result from internal atomic structure

N. Lindsley-Griffin, 1998

Cleavage - tendency to break along planes of weak bonds

N.Lindsley-Griffin, 1998

Mica cleaves along planes of the weakest bonds

N. Lindsley-Griffin, 1998

Fracture describes how a mineral breaks on an irregular surface rather

than along cleavage planes

N. Lindsley-Griffin, 1998

Types of fracture: Smooth Rough Splintery Conchoidal

© Houghton Mifflin 1998; Lindsley 2000

HardnessHardness

Mohs hardness scale: 1 = softest mineral; 10 = hardest

Diamond 10Corundum 9Topaz 8Quartz 7Feldspar 6 Steel file (6.5)Apatite 5 Glass (5.5- 6)Fluorite 4Calcite 3 Copper penny (3.0)Gypsum 2 Fingernail (2.5)Talc 1

Hardness -- the resistance to being scratchedMohs scale measures relative hardness, the ability of one mineral to scratch another

The 10 minerals of Mohs relative hardness scale

1 Talc 2 Gypsum

3 Calcite 4 Fluorite 5 Apatite

6 Feldspar7 Quartz

8 Topaz

9 Corundum 10 Diamond

N. Lindsley-Griffin, 1999

© Houghton Mifflin; N. Lindsley-Griffin, 1998.

LusterLuster

Luster - the appearance of a mineral in reflected light

Types of luster: Metallic Nonmetallic Pearly Vitreous Resinous Silky Dull Earthy

Metallic luster ofpyrite

Earthy luster oflimonite

Metallic Luster is characteristic of ore minerals and others that contain metal cations.

N. Lindsley-Griffin, 1998

Resinous luster in sphalerite

Pearly luster

in talcN. Lindsley-Griffin, 1999