Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Locked away in the vaults of Gem-A HQ in London is an assortment of breath-taking treasures that form Gem-A’s Gemstones and Minerals Collection. Here, Gem-A Gemmology Tutor, Pat Daly FGA, offers us a glimpse at some of the more unusual items in the collection.

Decades of collecting, bequests and acquisitions have led to the creation of the Gem-A Gemstones and Minerals Collection, which includes red beryl, banded fluorite, citrine, gypsum, peridot, zoisite and many more specimens that are worthy of conversations in their own right. Now, thanks to fantastic photography by Gem-A’s Henry Mesa, we can share some of these unique gemstones with you.

An example of a coral skeleton. Image by Henry Mesa, Gem-A.


Coral Skeleton

This example shows a classic coral skeleton: a branching, porous supporting structure produced by a colony of marine invertebrates.

Read more: Saltwater versus Freshwater Pearls

Precious coral, on the other hand, is a more compact and less porous material with a deeper saturation of colour. The sale of coral, like all organic gem materials, is subject to controls, which are designed to preserve marine faunal diversity and maintain stocks for the future.

A rough jadeite specimen. Image by Henry Mesa, Gem-A.


Also part of the Gem-A Collection is this cobble of rough jadeite which has been polished on one side to reveal the bright lustre modified by a dimpling, which is common on polished jadeite. This has a pleasing variation of white, green and lavender colours and a granular structure.

Read more: Jade and its Importance in China

 Jadeite is a polycrystalline gem material, composed of many small interlocking crystals. This structure gives it great strength and its resistance to breakage means that this gemstone can be made into delicate carvings, which are highly valued in China.

Emerald in Pyrite

This specimen (see cover photo) showcases well-formed crystals of emerald from Muzo, Colombia, in pyrite. Both minerals are formed from hot aqueous fluids circulating at high-levels and under great tectonic pressure in the earth’s crust.

A rough tanzanite crystal. Image by Henry Mesa, Gem-A.


The mineral zoisite is well-known as an abundant compound in some rock types, but it was of little significance to the gemstone trade until 1967, when tanzanite was found in a relatively small, two kilometre-wide belt in Tanzania. This well-formed crystal of tanzanite now forms part of the Gem-A collection, along with other cut and faceted tanzanites with deeper purple tones.

A box of 19 gemstones from the Anderson Collection, including a 30.82 carat beryl (centre). Image by Henry Mesa, Gem-A.

The Anderson Collection

This historically significant collection of gemstones was once owned by Gem-A founding father, Basil Anderson. In the 1980s, the entire collection of exceptional quality gems was destined for auction and risked being lost to the Association forever.


Gems from the Anderson Collection, including a 39ct aquamarine specimen (centre). Image by Henry Mesa, Gem-A.


Recognising this, an anonymous donor purchased the entire collection and donated it to Gem-A in 1986. Highlights include a specimen box containing 17 gemstones, including a 30.82 carat beryl, and a second box containing nine gems with a 39 carat aquamarine.

Cover image: Muzo emerald crystals in pyrite. Image by Henry Mesa, Gem-A.

This article was originally published in the Autumn 2018 issue of Gems&Jewellery (Volume 27, No.3).

Are you passionate about gemstones but new to the science of gemmology? Why not try one of our Introduction workshops.

Interested in taking your gemmological education further? Take a look at our Gemmology Foundation course

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