1. Identifying minerals
Ch 5 section 2

2. Bell ringer 10/29
What physical properties would you use to determine minerals?

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

4. Colored minerals

5. 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- deep reds and purples
Not a reliable way (on it’s own) to identify minerals

6. streak Color of mineral in powdered form
May use a streak plate (tile) to rub/scratch against
May grind with hands
May grind in a mortar and pestle
More reliable way of identification
Metallic- dark streak
Nonmetallic- light streak

7. Streak- do all minerals leave a streak?

8. luster Shinyness Is light reflected? Metallic Nonmetallic
If the mineral reflects light similarly to metals- polished look
Nonmetallic
Pearly, glassy, waxy, or brilliant shine to it

10. Cleavage vs. fracture
Cleavage
Fracture
Mineral splits into neat ridges leaving a smooth plane(s) behind
Splits occur at areas of weakness running parallel in the crystalline structure.
Looks cut
Not in even planes
Break off into jagged pieces leaving a rough texture
Uneven/irreagular fracture
- sandpaper
Fiberous fracture-
splinters
Conchoidal fracture-
curved

11. Cleavage breaks

12. Cleavage breaks

13. Fracture breaks Uneven breaks
Have curves or random pieces ( may feel gritty or dusty)
Appears to be BROKEN

16. hardness Ability to resist scratches
simple
difficult
Ability to resist scratches
Resistance to breaking (cleavage and fracture)
Resistance is due to its chemical structure and composition
Mohs hardness scale
Hardness is measured by the resistance which a smooth surface offers to abrasion.
The degree of hardness is determined by observing the comparative ease or difficulty which one mineral is scratched by another.

18. shape Minerals typical can take the shape of 6 basic crystal forms
Isometric/cubic
Tetragonal
Monoclinic
Orthorhombic
Hexagonal
triclinic

20. Density- i.e. specific gravity
Density (or Specific Gravity) is a very important property of minerals.
D= mass/volume.
It is measured using various apparatus and techniques which are covered in most mineralogy textbooks. These are:
Jolly Balance
Triple Beam Balance
Pycnometer
Heavy Liquids
Of these methods, the jolly and triple beam balance methods are best suited for mineral specimen work.
Simple/ easy to construct

21. Density- # atoms/ space
d= m/V

22. Special properties What do the following have in common? Florescence
Phosphorescence
Chatoyancy
Asterism
Double refraction

23. Fluorescence- minerals change colors when exposed to UV rays
Wavelengths reflected change due to some being absorbed causing a color change
Phosphorescence- minerals continue to give off reflected wavelengths of different colors.

25. Special features Chatoyancy- “cat eye”
Silky look
Asterism- star shape appears with reflected light
Double refraction- bending of light rays to produce a double image

26. Special properties
Magnetism – attractive forces due to the combination of e- in the atoms of the mineral
Contain iron (Fe)
Radioactivity- instability of the p+ and n+- in the atom-
energy is released