Citrine 

Citrine is a transparent, yellow variety of Quartz, ranging in color from pale to golden yellow, honey or almost brown, and may contain rainbow or sparkle inclusions. The name comes from the French word citron, meaning lemon.

Citrine is found in the Free state in South Africa, as well as in Namibia and Zimbabwe.

Chemical Formular :  SiO₂
Refractive Index :        1,54 – 1,55
Hardness :                  7 on the Mohs Scale
Crystal System :        Hexagonal crystal system