Upload
tim-corner
View
232
Download
0
Embed Size (px)
Citation preview
Rocks & MineralsNOTES
MineralA Naturally Occurring Naturally Occurring Inorganic Solid Inorganic Solid with a definite chemical chemical composition composition and crystaline structurecrystaline structure.
Mineral Properties & Identification
Crystal structure & chemical composition of minerals largely determine physical & chemical
properties used to identify
What causes minerals to have different physical properties?
their internal arrangement of atoms
The Main Physical Properties Used to Identify Minerals
Color
A poor indicator!
Minerals can be multiple colors
Many minerals are the same color
The Main Physical Properties Used to Identify Minerals
Streak
the powder form of a mineralmore reliable than color
Streak-Color of finely crushed residue or powder of a mineral
-When you write on chalkboard, you observe streak of chalk
-Streak of mineral usually consistent, making streak color more useful in identifying than mineral color
The Main Physical Properties Used to Identify Minerals
Luster
how light reflects off a mineral
metallic non-metallic
looks like a metal
looks earthy, waxy, greasy or brilliant
Luster- Shine from an unweathered mineral’s surface- Way a mineral looks in reflected
light- 2 groups of luster
Metallicshine like surface of clean stainless steel potExample: Pyrite & galena
Non-Metalliccan be glassy like black hornblende & quartzcan be pearly like muscovite mica
Hardness
The Main Physical Properties Used to Identify Minerals
resistance to being scratched
It is NOT the same as breaking!
For example: You can break glass easily with steel.However, steel will not scratch glass.
Hardness
The Main Physical Properties Used to Identify Minerals
Scratchability of minerals, not how easily it breaks
For example: Diamonds are hardest mineral, but if you
drop an unmounted diamond on a tile floor it will break
MOH’S SCALE OF HARDNESS
Hardness
Mineral Hardness
Mineral
1 (softest)
Talc 6 Orthoclase
2 Gypsum 7 Quartz3 Calcite 8 Topaz4 Florite 9 Corundum5 Apatite 10
(hardest)Diamond
- Quick way to determine relative hardness is to use piece of window glass1. If mineral scratches glass it is hard2. If mineral doesn’t scratch glass it is soft
Density-Each mineral has specific density or
narrow range of densities-Often stated as specific gravity,
which has no units-Specific gravity is density of mineral
compared to density of water-density is a good test to distinguish
gemstones, because it doesn’t harm samples
Cleavage- Tendency of mineral to break along
zones of weakness & form smooth to semi-smooth parallel sides or surfaces
- Cleavage surfaces can often be distinguished from sides without by having a shiner or more brilliant luster
- If minerals lack preferred zones of weakness, then it will demonstrate uneven breaking surface (fracture)
Fracture
The Main Physical Properties Used to Identify Minerals
the mineral breaks randomly
Crystal Structure
-Outward geometric shape of mineral, crystal form, reflect structure
-Orderly arrangement of atoms in mineral
-Any mineral can have many different crystal shapes
Other Mineral Properties- Some chemical properties of
minerals are used for identification- Reaction of a mineral with
acid