Destructive Gemstone Tests: Streak Testing
Streak testing is a destructive gemstone test rarely used by gemologists. Most gems leave no streak. Learn which gems do and what color they…
|Is a Variety of||Quartz|
|Colors||Golden brown (Tiger's eye); Blue (Hawk's eye); some pieces show both colors.|
|Enhancements||Bleaching, dyeing. Heat may create the eye effect.|
|Typical Treatments||Bleaching, Dyeing, Heat Treatment|
|Absorption Spectrum||Not diagnostic.|
o = 1.544; e = 1.553 (very constant). Uniaxial (+).
|Optic Sign||Uniaxial +|
Crocidolite, (blue asbestos,) alters to quartz, but while retaining its fibrous structure. This material is frequently stained by iron, giving it a golden brown color. We know this material as tigers eye. Unstained pieces, retaining their original blue color, are called Hawk’s Eye. There are also pieces with both colors.
Australia; China; Namibia; South Africa; England, UK; United States.