Sphalerite

Formula: ZnS

Colour: Yellow, light to dark brown, black, red-brown, colourless, light blue. green

Lustre: Adamantine, Resinous

Hardness: 3½ – 4

Specific Gravity: 3.9 – 4.1

Crystal System: Isometric

Member of: Sphalerite Group

Name: Originally called blende in 1546 by Georgius Agricola (Georg Bauer). Named Sphalerite in 1847 by Ernst Friedrich Glocker from the Greek σφαλεροζ “sphaleros” = treacherous, in allusion to the ease with which dark varieties were mistaken for galena, but yielded no lead.

Dimorph of: Wurtzite

Sphalerite, also known as blende or zinc blende, is the major ore of zinc. When pure (with little or no iron) it forms clear to white crystals (known as Cleiophane). Yellow to orange sphalerite is often called “golden sphalerite.” Red shades of sphalerite are known as Ruby Blende or Ruby Jack. As iron content increases, sphalerite forms dark, opaque submetallic crystals (known as Marmatite or Black Jack). Very rarely, green crystals owe their colour to trace amounts of Co. Sphalerite may also contain considerable Mn, grading into alabandite. It can also be Hg-rich and form a series with metacinnabar.