Moonstone

It cracks from a knock or a sudden change in temperature.

Potassium feldspar that unmixed into microscopically thin alternating layers as it cooled, so light scatters into a blue-white glow that floats and moves. It cracks from a knock or a sudden change in temperature. Sri Lanka has supplied the fine transparent material for centuries, slowly.

Slow cooling did all of it.

Sri Lanka and southern India have supplied the fine transparent material for centuries, which is one of the few genuinely long supply lines in this trade. The glow comes from orthoclase and albite unmixing into layers thinner than light as the crystal cooled. Slow cooling did all of it.

Two feldspars, interleaved, scattering light between them.

The glow comes from two feldspars, orthoclase and albite, that separated into microscopic alternating layers as the stone cooled and now scatter light between them. Roman writers called it solidified moonlight. It is brittle along its cleavages, so never boil it.

The Moon is the only planet Cancer rules.

The Moon is the only planet Cancer rules, and this is the stone the trade hands it. The glow is ordinary optics: orthoclase and albite unmixed into microscopic layers that scatter light back as a floating blue haze. Brittle along two cleavages, so never boil it and never drop it.

Borrowed light, which is the moon's entire arrangement.

The floating glow is called adularescence, caused by light scattering off alternating microscopic layers of orthoclase and albite that unmixed as the feldspar cooled. Sri Lanka and southern India have supplied the fine material for centuries. Borrowed light, which is the moon's whole arrangement.

Centipede inclusions: short parallel stress cracks, near diagnostic.

Potassium feldspar that unmixed as it cooled into alternating layers thinner than a wavelength, scattering light back as a soft blue haze. Look inside for centipede inclusions, short parallel stress cracks that are close to diagnostic. It is brittle along both cleavages and cannot take sudden temperature change.

The shine exists because it could not stay one thing.

One feldspar that unmixed into two as it cooled, orthoclase and albite in microscopically thin alternating sheets, and the floating blue glow is light bouncing between them. Look for centipede inclusions, short parallel stress cracks under the surface. The shine exists because it could not stay one thing.

It splits along planes you cannot see.

Potassium feldspar that unmixed as it cooled into layers thinner than a wavelength, scattering light into a glow that floats below the surface. The internal centipede markings are parallel stress cracks and are close to diagnostic. It splits from one knock, along planes you cannot see.

Look for centipedes inside, short parallel stress cracks.

Potassium feldspar that unmixed into microscopically thin layers as it cooled, scattering light into a glow that floats under the surface. Sri Lanka and southern India have supplied the fine transparent material for centuries. Look for centipedes inside, short parallel stress cracks.

It unmixed as it cooled. That is the whole trick.

Potassium feldspar that unmixed as it cooled, separating into layers thin enough to scatter light into a floating blue-white glow. Look for the centipedes, short parallel stress cracks inside the stone that are close to diagnostic. One knock cracks it internally, so keep it in a drawer.

Nothing is actually glowing.

Two feldspars unmixed into microscopically thin alternating layers as the crystal cooled, and the blue-white glow is light scattering between them. Nothing is actually glowing. It is brittle along its cleavages and cracks from a knock or a sudden change of temperature.

The glow floats under the surface and moves when you tilt it.

The glow floats under the surface and moves when you tilt it, which is light scattering off alternating microscopic layers of two feldspars that unmixed as the crystal cooled. Nothing is emitting anything. It is billowy, diffuse, and it comes apart if you drop it or shock it with heat.

Moonstone is carried for intuition, calm and sleep. Potassium feldspar that unmixed into microscopically thin alternating layers as it cooled, scattering light into a floating blue-white glow.. Tradition links it to the sacral, third-eye, crown chakra.

Moonstone is not faked often, but it is still worth checking. Real moonstone's sheen is soft, blue-white and directional. Opalite (glass) shows a warm orange glow when backlit and a cold blue glow in reflected light, plus round bubbles under a loupe.

A short rinse is fine for moonstone, then dry it.