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Transcript of Minerals
Between 2000-3000 have been identified
A few are "Native Elements" --- made from only one element
Most are compounds --- made from more than one element chemically bonded together
We identify 7 different mineral groups
Largest is Silicate Si, O
Others are Carbonates, Sulfides, Sulfates, Halides, Oxide, Native Element
Minerals are identified by their key characteristics or properties
Mineral are grouped by their composition or what element make up the minerals.
D - Definite chemical compound
I - Inorganic
N - Naturally occuring
O - Orderly arranged atoms---crystalline
S - Solid
an obvious property
is often unreliable
results from ability to absorb some wavelengths and reflect others
some minerals have characteristics colors
others vary due to chemical differences or impurities (atoms mixed inside the main elements)
Same mineral ---> different color
Different mineral ---> same color
Ability to scratch another mineral
Measured on Mohs scale from 1 (talc) to 10 (diamond)
Quartz (most common mineral and most dust particles) is 7
Describes how light reflects off the surface
Main categories are “metallic” and “non-metallic”Non-metallic includes dull, glassy, earthy, pearly, and others
Specific Gravity is the density of the mineral compared with density of water
All minerals have density (mass / volume), but some are very dense
Examples include galena, magnetite, and gold
We will use light, medium, and heavy by feel
Color of the powder when rubbed on a “streak plate” (unglazed porcelain)
May be same as hand-specimen or different
Cleavage and Fracture
Some minerals split along flat surfaces when struck hard--this is called mineral cleavage
Other minerals break unevenly along rough or curved surfaces--this is called fracture
A few minerals have both cleavage and fracture
There are other properties to look for as well.
Reaction to acid --- Calcite and other carbonate bubble in the presence of an acid
Magnetism --- Many Iron minerals are magnetic
Fluoresence --- Some minerals glow when placed under a UV-light
Salty Taste --- Halite has a istinctive salty taste ---> but we don't taste minerals in this lab!
Double Refraction --- When you look through Calcite, you will see words doubled
MORE TO COME LATER!!!
HOW DO YOU TEST HARDNESS?
FINGERNAIL = 2.5
GLASS = 5.5
If your mineral does not scratch your fingernail then it is less than 2.5
If your mineral scratches your fingernail but not the glass then it is between 2.5 and 5.5
If your mineral scratches glass then it is greater than 5.5