1. Identifying minerals
Ch 5 section 2

2. Physical properties Color Streak Luster Cleavage/fracture Hardness
Crystal shape
density

3. Color- Enough said…….
Established based on chemical composition in our crystalline structure- idiochromatic minerals.
Ions of certain elements are highly absorptive of selected wavelengths of light.
chromophores; elements which possess strong pigmenting capabilities.
and copper (Cu) are chromophores.
Sulfur- yellows
Cobalt- blue
Copper- orange
Chromium- deep reds/purples/ yellows
Iron- red/orange/brown
Manganese-
Not a reliable way (on it’s own) to identify minerals

4. Colored minerals Not a reliable way to identify minerals
Due to the atoms in it’s crystalline structure
Example-
Chromium- purples, dark oranges, and reds
Cobalt- deep blues
Manganese- deep reds and purples
Sulfur- bight yellows
Color can also be hidden due to weathering of minerals

5. streak
More reliable
Tested as a result of the powder left behind after a mineral scratches on a streak plate
Ceramic tile
Metallic minerals generally leave behind a darker streak than non metallic minerals
Not all minerals leave behind a streak (due to them being very hard)
Streak is still not the best test

6. Luster- shiny-ness All minerals have some form of luster
Metallic- looks like polished metal
Non metallic- has a brilliant, pearly, glassy, or waxy luster
Dull or earthy- looks like there is no luster at all

7. Cleavage breaks Nice neat geometric breaks
Looks as through someone “cut” a piece out
Mineral tends to break along a cleavage plane parallel to it’s weakness
Spot of weakness in the mineral due to it’s structure

8. Fracture breaks
Similar to a bone fracture- not a “clena break” but rough jagged pieces
Minerals may look jagged, rough like sand paper, curved, or even sandy with little pieces crumbling off
Uneven or irregular- broken wood or splinery fibrous fracture
Conchodial- curves along broken parts

9. Hardness-
Ability of a mineral to resist scratching based on what it can scratch
Result of the minerals strong internal sturcture due to the attractive force between the minerals bonds
Diamnonds has 4 strong bonds between C and O which is why it is the hardest mineral
Not resistance to breaks (cleavage or fracture)
Mohs hardness scale- compares minerals abilty to scratch one another based on 10 basic minerals

11. Crystal shape
Minerals take on 6 basic shapes and are a result of the minerals environment such as pressure, temperature, climate, ect
Isometric (cubic)
Tetragonal
Monoclinic
Orthorombic
Hexagonal
Triclinic
These are a result of a rotation about an axis (typically the y-axis) and unequal lengths

13. Density- specific gravity
D=m/v
Density- # of atoms in a crystal per amount of space the crystal takes up
Heavier atoms typically leads to minerals with greater densities per given volume
Triple beam balance, jelly balance, or liquid relationships are genrally the best ways to find density

14. Special properties- “glowing”
Fluorescence- ability to reflect wavelengths of light at bright colors due to being exposed to UV light
Calcite with the black light looked purple-blue
Phosphorescence- minerals that keep reflecting wavelengths of bright colors even after the UV light is shut off

15. Special properties- appearance
Chatoyancy- “silky” look where the mineral looks to have a soft silky surface
Caused by fibers in the mineral
Asterism- the mineral appears to have a star in the center when light is shown on it
Sapphires
Double refraction- bends light so that it looks like 2 images can be seen through the mineral (in crystal form)
Looks like being cross eyed and the image may be bent like looking through a glass of water
We passed around calcite

16. Special properties-energy
Magetism- attraction to minerals that contain Fe in their crystalline structure
React to the bar magnet
Radioactivity- some minerals give off energy due to the instability with their atoms p+ and n+- in the nucleus
U Ra- react to a Geiger counter