Minerals Identifier

Color

While the color of a particular specimen my be obvious, it is never the best major identifying characteristic.

 

Streak

The streak is the color produced when a mineral is powdered or drawn across a piece of unglazed porcelain. It is often quite different from the apparent color of the mineral, especially if it has a metallic luster.

  

Luster

Luster is the way light is reflected off the surface of a mineral. The terms used are:

  • metallic (like polished metal)
  • adamantine (like diamond)
  • vitreous (like broken glass)
  • resinous (like resin or wax)
  • pearly
  • silky
  • splendant (reflects an image brilliantly)
  • shining (reflects an image but not clearly)
  • glistening (reflects light but not an image)
  • glimmering (reflects from some points on the specimen)

 

Transparency

Minerals can be:

  • transparent (the outline of objects can be seen clearly through them)
  • semi-transparent (objects can be seen through them but are indistinct)
  • translucent (light passes through them but objects cannot be seen)
  • opaque (no light passes through)

 

HardnessHardness

Hardness measures how hard a mineral is to scratch or be scratched. It is measures on the Moh Scale:

Scale Comparison Test
1 Talc Powdered by finger nail
2 Gypsum Scratched by finger nail
3 Calcite Scratched by a copper coin
4 Fluorospar Easily scratched by a pocket knife
5 Apatite Just scratched by a pocket knife
6 Orthoclase Scratched by a steel file
7 Quartz Scratches a glass window
8 Topaz Easily scratches quartz
9 Corundum Easily scratches topaz
10 Diamond Cannot be scratched

Moh's Scale value 
between and

 

TenacityTenacity

Tenacity describes how easily a mineral can be cut. The terms used are:

  • sectile (easily cut with a knife)
  • brittle (crumbles if hit with a hammer)
  • malleable (flattens if hit with a hammer)
  • flexible (bends without breaking)

 

CleavageCleavage

Cleavage is the tendency of a mineral to break along planes of weakness. A good way to recognize cleave is to turn the specimen around in a good source of light and see if there is surface that will reflect the light as if the light were being reflected off a dull mirror.

Direction(s) of cleavage:

 

FractureFracture

Some minerals give a distinctive kind of break when hit with a hammer. The terms used to describe these breaks are:

  • conchoidal (shell-like)
  • subconchoidal (indistinct conchoidal)
  • even (leaving a flat surface)
  • uneven (leaving a rough, irregular surface)
  • earthy (leaving a dull, crumbly surface)
  • hackly (with sharp points)

 

DensityDensity (Specific Gravity)

The specific gravity of a mineral is its weight compared to water. An indication of specific gravity is how heavy a specimen feels:

Comparison Approximate
Specific Gravity
Lighter than sulfur less than 1.5
Sulfur 1.5
Quartz 2.5
Pyrite 6
Iron 7.5
Copper 9
Lead 11.5
Gold 15
Heavier than gold greater than 15

Specific Gravity between
and 

 




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