Sphalerite
Sphalerite,
also known as Blende, is one of the few minerals having six directions
of cleavage. If six directions are perfectly cleaved on a single
crystal, it forms rhombic dodecahedron. However, identifying the six
directions in a single piece is quite difficult because of multiple
twinning and the many directions. Only the abundant cleavage at
different directions are seen easily.
The name sphalerite has been derived from Greek word for treacherous
rock and Blend from German for blind or deceiving. The black and red
crystal forms of sphalerite are also nick named as Black Jack and Ruby
Jack. The iron content in it increases the darker shade and opaque
metallic crystals are known as Marmatite. Sphalerite is sometimes
difficult to identify from valuable minerals like galena, acanthite
and tetrahedrite.
Notable occurrences of sphalerite are Tri state area near Joplin,
Missouri; Rosiclare, Illinos; Elmwood, Tennessee, USA and Broken Hill,
Australia. It is also found in Italy, Spain, Burma, Peru, Morocco,
Germany and England. The hardness of the stone is 3.5 - 4 and specific
gravity is 4, heavier than average, but if compared to most metallic
minerals, it is light.
 
|
Name |
|
|
|
|
|
|
|
|
|
| Sphalerite |
3.5+ |
4.08-4.10 |
Cubic |
Perfect |
2.368-2.371 |
None |
0.156 |
None |
Variable to None |
|
