Moonstone
Moonstone is a variety of feldspar that displays a shimmering light effect or sheen that resembles moonlight, hence the name. The effect is called adularescence or schiller and is caused by the interference of light through lamellar layers within the stone. Stones with a bluish colour are the most sought after and therefore expensive; a cat's eye effect also occurs in some moonstone.
Source locations for Moonstone include: Australia, Brazil, India, Madagascar, Myanmar, Sri Lanka and USA.
Properties of the Gemstone and Additional Information
| Gemstone type: | Moonstone is a variety of feldspar, from the Alkali Feldspar Sub-group. |
| Crystal System: | Monoclinic |
| Chemical Composition: | Potassium aluminium silicate, K(AlSi3O8) |
| Colour: | Colourless, white, silvery-white, bluish-white, also occurs in yellow, green, brown and grey/black. |
| Lustre: | Vitreous |
| Pleochroism: | Absent |
| Dispersion: | Low |
| Hardness: | 6 to 6 1/2 on the Mohs' scale |
| Toughness: | Poor: Moonstone is a soft stone with perfect cleavage. It is also susceptible to thermal shock 'sudden temperature change' that may fracture the stone. |
| Cleavage: | Perfect |
| Density in gm/cc: | 2.56 to 2.59 |
| Double refraction: | Yes |
| Refractive index: | 1.518 to 1.526 |
Common Treatments
Moonstone is not normally treated.