Mineral Identification

Although nearly 2,500 minerals are known to occur within Earth's crust, most are rare with only about 100 occurring in abundance. Of those 100 minerals, fifteen make up the common rock-forming minerals and only some of the remaining minerals have any economic value.

Use the app below to identify your minerals.

Step 1

Is your mineral metallic or nonmetallic?

Step 2

Determine the hardness of your mineral. Using a glass plate, see if the mineral scratches it. Be careful, make sure the glass is on a table, do not hold in your hand. Firmly grasp your mineral and draw it over the glass. If the mineral powders, then use your fingernail to feel if the glass is scratched.

Does your mineral scratch glass?

Step 5

Use chart below to determine your mineral:


Mineral

Description


Hematite
specular variety
Fe2O3
Steel-gray to black to brown in color
micaceous
H: 5-6.5
G: 3.3-3.4
reddish-brown streak

Pyrite
FeS2
Pale brass-yellow in color
often occurs in cubes
H: 6-6.5
G: 5
green-black to brown-black streak

Magnetite
Fe3O4
Strongly magnetic
black in color
commonly occurs in masses or single, octahedral crystals
H: 6
G: 5.2
black streak

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity

Step 2

Determine whether your mineral is light-colored or dark-colored.

Is your mineral light-colored or dark-colored?

Step 5

Use chart below to determine your mineral:


Mineral

Description


Galena
lead ore
PbS
Silvery in color
heavy
H: 2.5
G: 7.6
perfect cubic cleavage
lead gray streak

Chalcopyrite
CuFeS2
Brass-yellow in color
tarnishes to purple
H: 3.5-4
G: 4.5
green-black streak

Sphalerite
zinc ore
ZnS
Brown, black, or yellow in color
6 directions of cleavage
H: 3.5-3.5
G: 4
yellow, brown or white streak that has a rotten egg smell

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity

Step 3

Determine the hardness of your mineral. Using a glass plate, see if the mineral scratches it. Be careful, make sure the glass is on a table, do not hold in your hand. Firmly grasp your mineral and draw it over the glass. If the mineral powders, then use your fingernail to feel if the glass is scratched.

Does your mineral scratch glass?

Step 3

Determine the hardness of your mineral. Using a glass plate, see if the mineral scratches it. Be careful, make sure the glass is on a table, do not hold in your hand. Firmly grasp your mineral and draw it over the glass. If the mineral powders, then use your fingernail to feel if the glass is scratched.

Does your mineral scratch glass?

Step 4

Determine whether your sample has cleavage. Does your mineral have cleavage?

Step 5

Use chart below to determine your mineral:


Mineral

Description


Augite
Ca, Mg, Fe, Al silicate
Dark green to black in color
Cleavages at nearly right angles
Short, prismatic 8-sided crystals
H: 5-6
G: 3.3

Hornblende
Na, Ca, Mg, Fe, Al silicate
Dark green to black in color
2 cleavages at 60o
H: 5-6
G: 3.3
long, prismatic 6-sided crystals

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity

Step 5

Use chart below to determine your mineral:


Mineral

Description



Garnet
Ca, Mg, Fe, Al silicate
Silvery in color
heavy
H: 2.5
G: 7.6
perfect cubic cleavage
lead gray streak

Olivine
(Fe, Mg)2SiO4
Olive-green in color
2 cleavages at 60o
H: 6.5-7
G: 3.3-4.4
Translucent to transparent
Commonly occurs in granular aggregates with a sugary texture
Conchoidal fracture

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity

Step 4

Determine whether your sample has cleavage. Does your mineral have cleavage?

Step 5

Use chart below to determine your mineral:


Mineral

Description


Sphalerite
Zinc ore
ZnS
Brown, black, or yellow in color
6 cleavage directions
Yellow, sulfurous smell to streak
H: 3.5-4
G: 3.9-4.1
L: resinous
S: yellow

Biotite
K(Mg, Fe)3AlSi3O10
Black-brown in color
1 perfect cleavage
H: 2.5-3
G: 2.7-3.1
L: Vitreous
Thin plates are elastic
S: white

Chlorite
Mg, Fe, Al silicate
Green in color
1 perfect cleavage
H: 2-2.5
G: 2.6-2.9
Nonelastic scaly masses
S: white to pale green

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity

Step 5

Use chart below to determine your mineral:


Mineral

Description


Hematite
earthy variety iron ore
Fe2O3
Reddish-brown in color
Cleavage is not obvious
H: 5
G: 5.3
S: reddish brown
L: usually earthy
May show rounded forms

Kaolinite
clay
Al4Si4O10(OH)8
White to red in color
Earthy masses
H: 1
Earthy odor and luster
Behaves plastically when wet
Resembles chalk

Limonite
iron ore
Fe2O 3H2O
Yellow to brown in color
Earthy masses
H: Earthy masses
S: yellow-brown
G: 3.3-3.4

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity

Step 4

Determine whether your sample has cleavage. Does your mineral have cleavage?

Step 5

Use chart below to determine your mineral:


Mineral

Description


Orthoclase
potassium feldspar
KalSi3O8
Variable color, most are creamy white or pinkish
H: 6
G: 2.5
C: 2 good at nearly right angles
L: vitreous or pearly

Plagioclase
K-spar
NaAlSi3O8 to
CaAl2Si2O8
Creamy white or gray in color
H: 6
G: 2.6-2.8
C: 2 good at nearly right angles
L: vitreous or pearly
striations on cleavage faces

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity

Step 5

Use chart below to determine your mineral:


Mineral

Description


Quartz
SiO2
Variable in color
May occur as 6-sided crystals
H: 7
G: 2.7
S: reddish brown
L: translucent to milky
Conchoidal fracture
Varieties: milky (white and opaque), smoky (gray to black), rose (pink), amethyst (purple)

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity

Step 5

Use chart below to determine your mineral:


Mineral

Description


Fluorite
CaF2
Variable color (yellow, blue, green, or purple)
H: 4
G: 3.2
C: 4 perfect, triangular cleavage faces
L: transparent to translucent
cubic crystals

Dolomite
CaMg(CO3)2
White, gray or pink in color
H: 3.5-4
G: 2.8
C: rhombohedral, 3 directions
Reacts with HCl is powdered

Barite
BaSO4
Clear, milky white, or light-yellow in color
H: 3
G: 4.5 heavy
C: 2 directions at right angles
Forms thick plates

Calcite
CaCO3
Variable in color
H: 3
G: 2.7
C: 3 perfect; rhombohedral
Reacts with HCl

Halite
NaCl
Clear or milky white in color
H: 2.5
G: 2.2
C: perfect cubic
Tastes salty
Soluble in water

Muscovite
KAl2(AlSi3O10)(OH)2
Colorless to slightly gray in color
H: 2-2.5
G: 2.5-3
C: 1 perfect direction
Occurs in thin, transparent elastic sheets

Gypsum
CaSO4 2H2O
Colorless to white in color
H: 2, easily scratched with fingernail
G: 2.3
C: 1 perfect, 2 good
splits into slabs
Varieties: selenite (colorless), satin spar (fibrous, silky), alabaster (aggregates of small crystals)

Talc
Mg3Si4O10(OH)2
White, gray, green, pink, or brown in color
H: 1, easily scratched with a fingernail
G: 2.7
C: 1 perfect
L: pearly or greasy
Has a soapy feel

H=hardness // F=fracture // L=luster // S=streak // G=specific gravity