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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.
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