Moonstone (iridescent peristerite-oligoclase feldspar) (Chupa Pegmatite Field, Mesoproterozoic, 1.75 to 2.10 Ga; at or near Chupa Bay, northwestern Karelia, far-nw Russia) by James St. John, on Flickr
Peristerite is primarily oligoclase with a complex mixture of feldspars. It has iridescence that is either blue or white.
| Data | Value |
|---|---|
| Name | Peristerite |
| Is a Variety of | Albite |
| Colors | White, blue. |
| Fracture | Conchoidal, uneven, splintery |
| Hardness | 6-6.5 |
| Cleavage | Perfect 2 directions |
| Crystallography | Triclinic. |
| Refractive Index | 1.531-1.550 |
| Birefringence | 0.007-0.011 |
| Absorption Spectrum | Not diagnostic. |
| Pleochroism | None. |
| Optics | Biaxial (-). 2V = 82°. |
| Optic Sign | Biaxial - |
| Luster | Vitreous. |
| Specific Gravity | 2.62-2.67 |
| Transparency | Transparent. |
| Phenomena | Schiller. |
Comments
Compositions in the calcic oligoclase range (Ab76) cool and unmix to an inhomogeneous mixture of two feldspars, producing a Schiller, which in the case of peristerites is white or bluish. The effect seems to emanate within the body of the feldspar as a kind of glow.
Name
Peristerite is from the Greek word peristera, meaning pigeon.
Occurrence
Peristerite is well known from Ontario, Canada, where it is very abundant. It is also found at Kioo Hill, Kenya: S.G. 2.63; a=1.531: β= 1.535; γ= 1.539.
With sheen reminiscent of moonlight, moonstone is treasured across civilizations. Our moonstone buying guide can help you pick one perfect for…
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