Quartz
There are many varieties of crystalline quartz, the following are examples of those referred to with quartz in their name. Rock crystal is sometimes referred to as simply 'quartz'.
Cat's eye quartz: A white, grey, green, yellow or brown chatoyant material, cut en cabochon to produce cat's eye quartz.
Green quartz: Known as prasiolite and vermarine, is produced by heat-treating amethyst.
Smoky quartz: A transparent stone with a smoky yellow, brown to black colour caused by natural or artificial radiation.
Rock crystal (quartz): A clear colourless quartz that is faceted.
Rose quartz: Pink in colour; clear stones are faceted. Stones that have asterism are cut en cabochon to make six-rayed star
Rutilated quartz, Has radiating needles of rutile and sometimes included crystals, they are highly prized collector pieces.
Properties of the Gemstone and Additional Information
| Gemstone type: | Varieties of crystalline quartz. |
| Crystal System: | Trigonal, occuring as hexagonal prisms. |
| Chemical Composition: | Silicon dioxide, SiO2. |
| Colour: | As described above for each variety. |
| Lustre: | Vitreous |
| Pleochroism: | Dichroic weak: varations of the same colour. |
| Dispersion: | Low |
| Hardness: | 7 on the Mohs' scale. |
| Toughness: | Good |
| Cleavage: | None |
| Density in gm/cc: | 2.65 |
| Double refraction: | Yes |
| Refractive index: | 1.544 to 1.553 |
Common Treatments
Green quartz (prasiolite) is produced by heat-treating violet amethyst.
Rock crystal may be irradiated to produce smoky quartz..