Moonstone

Moonstone is a little difficult to write about, as there are multiple ‘types’ – some of which are not really the same type of material.

Of the most common mentioned, you may see ‘Rainbow Moonstone’, ‘Moonstone’, ‘Peach Moonstone’, ‘White Moonstone’, ‘Blue Moonstone’, or ‘Black Moonstone’.

You’ll find more information at the bottom of the page.

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Appearance, Uses and History

Moonstone is a little difficult to write about, as there are multiple ‘types’ – some of which are not really quite the same type of material.

Of the most common mentioned, you may see ‘Rainbow Moonstone’, ‘Moonstone’, ‘Peach Moonstone’, ‘White Moonstone’, ‘Blue Moonstone’, or ‘Black Moonstone’.

Moonstone, peach Moonstone and black Moonstone are varieties of the same material, with their colours altered slightly by mineral inclusions.

White Moonstone is generally a gem quality version of the above, with a type of chatoyance that give it almost a cats eye or asterism effect.

Rainbow Moonstone and Blue Moonstone, on the other hand, are a different material – closer to Labradorite. They are white, with occasional inclusions of Schorl (black Tourmaline), but possess an interesting play of colour. Blue Moonstone has, naturally, quite a bright blue flash.

Rainbow Moonstone, on the other hand, can show several colours, with greens, yellows and blues being the most common.

A more appropriate name might be ‘white Labradorite’, but arguably the Feldspar family is so complex it may be easier to just leave the public with the old name…

Moonstone is, obviously, a trade name – it is likely applied to other varieties of feldspar incorrectly sometimes – particularly peristerite, antiperthite, and anorthoclase.

Locales

Moonstone occurs worldwide, locales including Brazil, Japan, India, Mexico, Poland, Russia, Sri Lanka, and the USA.

Particularly fine gem quality specimens are found in Sri Lanka.

Mineralogy

Chemistry
A sodium potassium aluminium silicate, with the formula (Na,K)AlSi3O8.
Colours and Variations
Various colours – white, cream, brown, black, grey, blue, pink, peach background tones. High quality specimens have a bright flash of colour which can include whites, blues, yellows, greens and more.
Streak
White
Luster
Opalescent
Fracture
Uneven to conchoidal
Transparency
Translucent to transparent.
Crystal habit
Monoclinic
Mohs hardness
6 – 6.5
Specific Gravity
2.56-2.61
Fluorescence
Typically inert in longwave UV, sometimes orange in shortwave.
Easiest testing method
Common Treatments
None.

Hazards and Warnings

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis.

When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

Translations

As moonstone is a colloquialism, it may not translate well into other languages.

Arabic:

  • حجر القمر

Hindi:

  • मूनस्टोन

Portuguese:

Bengali:

Indonesian:

Punjabi:

English:

  • moonstone
  • hecatolite

Italian:

  • pietra di luna

Russian:

  • лунный камень

French:

  • pierre de lune

Japanese:

  • ムーンストーン

Spanish:

  • piedra de la luna

German:

  • Mondstein

Korean:

  • 월장석

Thai:

  • มูนสโตน

Gujurati:

Mandarin and Traditional Chinese:

  • 月光石

Urdu:

Further Reading / External Links