Properties of Minerals

1. Color• Easy to see but is least reliable

property for ID–many different minerals are same

color (calcite, quartz, dolomite)

–same mineral can come in many colors (quartz can be pink, white, clear, purple, yellow)

The Many Colors of Quartz

Amethyst

CitrineSmoky Quartz

Rose Quartz

Rock Crystal

Many Different White Minerals

Minerals Come in Many Different Colors

2. Luster• How mineral shines in reflected light

–metallic: like polished metal

–non-metallic: all others• vitreous: glassy

• pearly

• dull

Luster

Metallic Dull

VitreousPearly

3. Streak• Color of powdered form of mineral

–not always same color as mineral

–found by rubbing mineral on unglazed tile

–non-metallic minerals usu. have white streak

4. Cleavage

• Mineral splits along flat surfaces–can cleave in 1,2 or 3

directions

Cleavage

5. Fracture

• Mineral breaks along non-cleavage surfaces–rough edges

–conchoidal fracture: smoothly curved like inside of a shell

Fracture

6. Hardness

• Mineral’s resistance to being scratched

• Moh’s Scale of Hardness–compares minerals from softest

(talc=1) to hardest (diamond=10)

Moh’s Scale of Hardness

• 1. Talc

• 2. Gypsum

• 3. Calcite

• 4. Fluorite 8. Topaz

• 5. Apatite 9. Corundum

• 6. Feldspar (ruby)

• 7. Quartz 10. Diamond

Hardness Continued

• Scratch Test• fingernail scratches mineral =2

• penny scratches mineral =3

• steel nail or file “ “ =4

• mineral scratches glass =6

7. Specific Gravity

• How dense the mineral is

• metallics usu.>5

• non-metallics usu.<3

Specific Gravity

Metallic minerals

are high Non-metallic

minerals are lower

8. Acid Test

• Only CARBONATE minerals fizz in weak acid

• calcite

9. Crystals

• Not all minerals show crystals

• when minerals do show crystals, they usu. have a characteristic shape

Quartz Crystals

10. Special Properties• Taste (rock salt)

• Smell (sulfur)

• Fluorescence : glows in UV light

• Radioactivity (uranium)

• Double refraction: two images show through clear mineral (calcite)

Special Properties

Magnetite-magnetic Uraninite-

radioactive

Sulphur-smelly

Some Common Minerals

Galena

Cleavagein 4 directions

Metallic

Feldspar

Cleavage

Pinkish

Graphite

Metallic

Very Soft

Lubricant

Magnetite

Limonite

Quartz

Aquamarine:Click for sample mineral lab.