A-Z of Gemstones: M

Posted on the 6th November 2016

A-Z of Gemstones: M: Moonstone, Morganite

MOONSTONE

Moonstone is a phenomenal variety of the orthoclase species that belongs to the wide group of feldspars. 

Moonstones are praised for their widely recognised phenomenon called adularescence which refers to the sheen created by the thin layers inside the stone that make the light scatter.

Moonstones come in white, peach, green, brown and grey and the most valuable ones are near-transparent with a strong blue sheen. 

Moonstones are usually cut into cabochons, beads and sometimes faceted stones.

Moonstone’s lustre is vitreous; it rates 6-6.5 on the Mohs scale which makes it suitable for jewellery that has secure settings to protect the stone from scratching.

The main sources for moonstones are: Sri Lanka, India, Australia, Germany, Brazil, Myanmar, Madagascar and Mexico.

There are no known treatments for moonstones and it has not yet been synthesized in the lab.

Materials that are most commonly used to imitate moonstones are glass and plastic.

MORGANITE

Morganite was discovered in 1911 in Madagascar and was named after the famous American banker J.P.Morgan who was a gem enthusiast.

Morganite is the pink variety of the beryl species. It can be light to medium pink or an orangey pink salmon colour which is caused by the presence of manganese trace elements.

Depending on the transparency of the stone which can be anything between transparent to almost opaque, morganites are cut into faceted gems, cabochons and beads.

Usually, morganites look clean to the naked eye.

Morganite’s lustre is vitreous; it rates 7.5-8 on the Mohs scale which makes it suitable for jewellery that has secure settings to protect the stone from wear.

The origin of the finest quality morganites is Madagascar but mining is limited. Other main sources of morganite are: Brazil, Afghanistan, Mozambique, Namibia and the U.S.A.

Almost all morganites on the market undergo treatment to improve their colour. Heat treatment eliminates the yellow and orange hues making the colour of the stone a purer and more desirable pink.

Morganite has been synthesised and the lab-grown stones have similar chemical property to natural morganites but their value is significantly lower so they should always be disclosed as synthetic.

Materials that are most commonly used to imitate morganites are glass and plastic.