Moon Stone

Moonstone is a feldspar, generally an alkali feldspar in which two phases, typically orthoclase and albite, have separated into alternating microscopic layers as the crystal cooled slowly. Light entering the stone is scattered by these layers, and because the layers are of a thickness comparable to the wavelength of light, the scattering is preferential toward the blue end. The result is the floating blue-white sheen called adularescence, which appears to lie beneath the surface and to move as the stone is turned.

The name comes from Mount Adular in Switzerland, an old locality for the material. The best modern source has been Sri Lanka, with blue-sheen material from there and from Burma; rainbow moonstone, widely sold, is a labradorite rather than an orthoclase feldspar and is a different mineral marketed under the moonstone name.

The mechanism is the same class of phenomenon as the play of colour in opal and the schiller of labradorite: structural optics rather than pigment. Nothing in the stone is blue. This matters for the tradition, because the sheen's resemblance to moonlight is a genuine optical fact and the inference from it (that the stone is lunar, feminine, tidal, connected to cycles and to dreaming), is association by appearance. The resemblance is real; everything built on it is analogy.

Moonstone is soft for a ring stone at around 6 to 6.5, with two directions of perfect cleavage, and it chips readily. Feldspar is the most abundant mineral group in the earth's crust, so the material is common; only the sheen is uncommon.

Moonstone's associations are almost entirely modern, and the exceptions are worth isolating from the general claim of ancient reverence.

There is a genuine Indian tradition. Moonstone is chandrakanta in Sanskrit sources and is associated with the Moon; in jyotisha it functions as a substitute or secondary stone for Chandra, the Moon, where pearl is the primary navaratna gem. It is regarded in Indian practice as auspicious and is a traditional wedding gift. That is a real, continuous and documented tradition.

The Roman claim frequently printed, that Romans believed moonstone was formed of solidified moonlight, traces to Pliny's discussion of a stone he calls selenites, which he describes as containing an image of the moon that waxes and wanes with it. Whether selenites is moonstone, or selenite gypsum, or something else, is not determinable, and the confident attribution to moonstone is a modern gloss on an ambiguous passage. It is the same name problem that runs through all ancient gem identification.

The rest (intuition, emotional soothing, new beginnings, travel protection, the sacral and crown centres), belongs to the twentieth and twenty-first century crystal-healing literature, which reached its present form through Art Nouveau jewellery's revival of the stone around 1900 and then through the metaphysical publishing of the 1970s onward. The chakra assignments in particular cannot be older than the Western synthesis of chakra material, which is late nineteenth and twentieth century.

Moonstone was not on the 1912 list. It appears as a June alternative in later revisions alongside pearl and alexandrite.