MATERIAL

HARDNESS
(MOHS SCALE)

GRAIN
SHAPE

SPECIFIC
GRAVITY

COLOR

FREE SILICA
CONTENT

FREE IRON
CONTENT

DURABILITY

CORN COBS
WALNUT SHELLS

2
3

Cubical
Cubical

1.3
1.3

Tan
Light Brown

None
None

None
None

Good
Good

PLATIC MEDIA
GLASS BEADS

3 to 3.5
4.5

Angular
Spherical

1.2
3.0

White
Crystal

None
None

< .002%
None

Excellent
Good

SAND
COPPER SLAG

5
6 to 8

Rounded
Spherical

1.75
3.16

Tan
Black

90% to 100%
None

< 1%
< 1%

Fair
Good

STEEL SHOT
STEEL GRIT

6 to 7
6 to 7

Spherical
Angular

4.80
1.75

Steel Grey
Steel Grey

None
None

99%
99%

Excellent
Excellent

FLINT SHOT
GARNET

6 to 7
7

Spherical
Spherical

1.75
4

White
Pink

90% to 100%
< 2%

< 2%
< 1%

Good
Good

QUARTZ
ZIRCON

7
7.5

Sperical
Cubical

2.65
4.58

White
Tan

100%
< 5%

< 2%
< 1%

Fair
Good

EMERY
ALUMINUM OXIDE

8
9

Angular
Cubical

4.00
3.80

Reddish Brown
Brown

< 1%
< 1%

< 1%
< 1%

Good
Very Good

SILICON CARBIDE
DIAMONDS

9
10

Cubical
Cubical

3.13
3.50

Black
Yellow

< 1%
< 1%

< 1%
< 1%

Good
Excellent