Mineral Type - Quartz - Citrine
Toprock only sells natural Citrine. We DO NOT supply heat treated citrine. All of our products are 100% natural. Exceptional African citrines are known from Zambia (available in a polished format), as well as the Lwena Citrine deposits in the Democratic Republic of Congo. We also get a limited supply of polished citrine crystal points from Madagascar but they are pale in comparison to the exceptional colours from Zambia and Congo.
Etmologty
From citrina (colour as yellow as citron).
Physical Properties
Lustre: Vitreous
Colour: Yellow - Orange - Smokey
Hardness: 7 on Mohs scale
Chemical Properties
Formula: SiO2
Elements listed: O, Si
Crystallography
Crystal System: Trigonal
Synonyms
Bohemian Topaz, Citron, Kundalini Quartz, and Lemon Quartz
Comments
The physical cause of the colour is still under debate. At least some citrine is coloured by aluminum-based and irradiation-induced colour centers related to those found in smoky quartz (Lehmann, 1972; Maschmeyer et al., 1980). Accordingly, transitions to smoky quartz ("smoky citrine") exist, many citrines show smoky phantoms. Like smoky quartz, these types of citrines pale when heated above 200-500°C and turn yellow again when irradiated (Lehmann, 1970). There appear to be at least two types of yellow Al-based colour centers with different thermal stability (Schmetzer, 1988). Since the yellow colour centers are often more stable than the smoky colour centers, some smoky quartz can be turned into citrine by careful heating (Nassau and Prescott, 1977). Natural citrine as well as citrine produced by heating smoky quartz is dichroic in polarized light. It has also been suggested that iron is the cause of colour, as artificial crystals grown in a iron-bearing solution turn out yellow. However, the dichroic behavior of the lab-grown crystals differs from that in natural citrine (Rossmann, 1994).