Professional gemmologists are often asked similar questions, like what is the rarest stone they have encountered and is there anything ‘new’ left to discover. The answers, especially to the latter, are not easy to formulate, and there are factors that a gemmologist must unpack to provide a suitable response. Here, Gem-A Tutor Pat Daly considers how likely it is that we will discover a ‘new’ gem material and what that might look like in reality… 

This question is not easy to answer for several reasons. When we say that gemstones are found, we usually mean that they have been noticed by people with access to well-established gem and jewellery markets. They may have been known locally for a long time. In some cases, the locations of gemstone mines were forgotten, and they had to be rediscovered. For example, jadeite from Guatemala was used in Central America for hundreds of years before sources were relocated in the 1950s to 1970s. 

Nephrite jade photographed by Pat Daly.

Gem prospectors have often been helped by seeing what local people have found.

We cannot know what might be discovered in the coming decades, but consideration of the many gem species and varieties which have been discovered in the past can help us to decide the likelihood of finding them in the future. 

The history of gemstones and jewellery reaches back into prehistory. Biogenic materials such as ivory, bone and shell, and distinctive rocks, like obsidian and jades, were used before the establishment of recognisable civilisations. Many other materials have been used for 2,000 years and more, such as quartz gems, lapis lazuli, turquoise, emerald and corundum, and their original discoveries are hidden from us. 

Tanzanite gemstone photographed by Henry Mesa.

Formal descriptions of gemstones during the 19th century, as the sciences developed, provide reliable dates, although they may not give those of first discovery. They gave details of chemistry, physical properties and crystallography, so that gem species could be properly defined, and gem varieties could be related to their correct mineral groups. Notable stones which made their first appearance in this century included the colour-change alexandrite variety of chrysoberyl in the 1830s and bright green demantoid garnets, both from Russia and the emerald-green hiddenite variety of spodumene from the USA. 

As well as the advent of previously unknown gem varieties, new sources of well-known gemstones were found. The greatest of these was the diamond deposits in South Africa. Before about 1870 all diamonds had come from India, Brazil and Borneo. The new mines provided quantities which could satisfy demand in industrialised countries, in which increasing numbers of people could afford to take an interest in gemstones.

Benitoite in matrix photographed by Henry Mesa.

Additional sources of diamonds were found during the following century, starting with Namibia in 1906, followed by mines in other African countries, Russia and Australia. The production of gem diamonds a century after the first African discovery was about 100 times greater than before. 

Other stones found in the first decade of the 20th century included sapphire-blue benitoite, a stone from just a couple of mines in California. Despite its rarity, this stone has retained its desirability and is as celebrated now as when it was introduced to the gem market. Kunzite and morganite, the pink varieties of spodumene and beryl, respectively, were found before 1910.

Sinhalite gemstone photographed by Pat Daly.

As the century progressed, more new stones were traded. Of those species and varieties which are well-known, at least to jewellers and gemmologists, 20 or more were discovered during the 20th century, besides many more which may be known only to keen collectors. They include commercially important varieties such as the lovely blue to purplish tanzanite and bright green tsavorite garnet, both found in the 1960s. Vividly coloured Paraiba tourmalines from Brazil astonished the trade in the 1980s, and they were joined by similar stones from Nigeria and Mozambique in the Early years of this century. 

Other interesting stones are also worthy of attention, such as transparent red beryls, fine sapphire-blue kyanites, bright green, chrome-coloured tourmalines and diopsides and colour-change diaspore, a mineral which was previously unknown in gem quality. Opaque stones included charoite, a Russian material with an unmistakable purple, silky appearance, and sky blue larimar from Dominica.

A group of red beryl pear-shaped gemstones from the Gem-A Archives.

There were new garnet varieties, apart from tsavorite. Some stones rival the red-to-green colour change of alexandrite, and iridescent garnets were found in Nevada, Mexico and Japan. 

A few of the new stones changed colour when irradiated with ultraviolet. Some hackmanite, a variety of sodalite, changes from pink to amethystine purple when held in sunlight and fades when kept away from it. The colour of tugtupite, a pink stone from Greenland, also intensifies in sunlight and slowly fades when out of it.

Amongst other particularly interesting stones are ekanite, one of the few radioactive materials cut as a gemstone, taaffeite, the only mineral first discovered as a faceted stone and which was bought from a Dublin jeweller in 1945, brazilianite, a pleasing greenish-yellow gemstone named after its country of origin, and sinhalite, whose similar properties led to its confusion with peridot before it was recognised as a new mineral. 

Rough brazilianite photographed by Henry Mesa.

We have now entered a new century and may look forward to the introduction of new gem materials. Some have already appeared. A commercially important source of diamonds in Canada is now mined, a new gem mineral, pezzottaite, from Madagascar, and two rare stones which had been described in the last century but were not seen as faceted stones before the millennium. Painite, a pink to reddish brown stone, was one of the rarest minerals known in the mid to late 20th century but cut stones became available from two localities in Myanmar. Grandidierite was described in 1902, but the pleasing transparent green gem-quality stones were not available before 2003.

Pezzottaite gemstone photographed by Henry Mesa.

It is not possible to predict the future. At some time, all accessible gem deposits may be found, worked and exhausted, but it is most unlikely that we have reached that situation. New gemstones have been discovered recently in countries, such as Myanmar and Sri Lanka, which have been worked for thousands of years, and new areas, such as Antarctica and the arctic regions of the northern hemisphere, areas covered by bogs, forests and deserts remain to be explored. Based on what has happened in the past, we may look forward to future finds of gemstones; some will be familiar, but others may be wholly unexpected.

Main image: rough gemstones courtesy of Unsplash, royalty free.

Considering the high costs associated with diamonds, finding a suitable birthstone gift for the month of April can be a challenge. The trick is to look deeper into the subject of gemmology to find white and colourless gemstones that can serve as fantastic alternatives. Here, Gem-A Tutor Pat Daly shares his thoughts on this quest for more budget-conscious options…  

Birthstones are gem materials associated with the different months of the year and are sometimes thought to bring good luck to those who wear them. There is, however, no universally accepted list of birthstones. Several have been used since ancient times, and they do not agree in all details. In different traditions sapphire, for example, is variously assigned to April, July, August and September.

The linking of stones with months goes back more than an estimated 3,500 years to Tibetan and Indian traditions, and it continued during classical Greek and Roman times, the medieval period and to the present day. Throughout history, scholars have tried to classify gemstones, originally by their appearance and then by their durability and density. Identification methods were limited until their chemical compositions and crystal structures were better understood in the 19th century. This means that the names given to gems in past centuries may not be the same ones we would use today, and a name might now be applied to a different stone. We cannot always be certain that we know the identity of the stones listed in ancient documents. Nor can we be sure that the months we recognize span the same parts of the year as the time periods used in the distant past. 

A selection of zircon gemstones, including a colourless option (bottom left), from the Gem-A Archives.

Details of calendars have changed over time. Modern systems offer alternative stones of different values, which increases the potential for choice, and they include varieties, such as alexandrite and tanzanite, which were unknown before the 19th century.

Therefore, there are good reasons to substitute another stone for a listed one that may be too expensive or not satisfy a customer’s taste. 

Diamond is commonly considered a white stone, though most of them incorporate a hint of yellow and may be of any colour. Stones that are white or nearly so are probably the best alternatives to diamonds. Those which are most often suggested are sapphire, rock crystal, topaz and opal. 

Diamond is valued for a unique combination of properties. It may be completely white and perfectly transparent. Its lustre is the brightest that can be seen on non-metallic materials and has been chosen as the standard against which other stones are compared. Its high refractive index is expressed as the brilliance for which well-cut stones are famed, its property of dispersion, or fire, is the highest of all natural white gemstones which are commonly used in jewellery, and its single refraction means that there is no tendency for facet edges seen through the stone to appear blurred or out of focus. 

White beryl from Brazil, photographed by Henry Mesa.

Any material may be broken, but diamond has a reputation for toughness, and it is the hardest of all gemstones. The rarity and value of diamond means that cutters can afford to spend the time to cut flat, well-polished facets at the correct angles, to produce fashioned stones which are sufficiently well proportioned and symmetrical to display its desirable optical properties, and it is durable enough to preserve the sharp edges and corners, and unscratched facets, which are needed for this purpose.

No other stone can compete with this combination, but they do supply some of these features and their lower values mean that they are available in much larger sizes than the diamonds which most people can afford. 

Rough rock crystal specimen, photographed by Henry Mesa.

Topaz and the rock crystal variety of quartz are available in large, transparent, inexpensive pieces which may be faceted or, in the case of rock crystal, fashioned into table ornaments. Both are hard, though they do not compare well with diamond in this respect, and they are reasonably tough. Neither displays much fire, however, and their relatively low refractive indices mean that they cannot show brilliance at the range of viewing angles which is possible for diamond. In addition, their low value prevents lapidaries from investing the time needed to get the best optical effects from them, so the quality of polishing tends to be commonplace.

Faceted quartz with a pyrite inclusion, photographed by Henry Mesa.

White sapphires are more expensive. Good quality stones may cost hundreds of pounds per carat. The refractive index of sapphire is high enough to make a good brilliance and lustre possible on well-polished stones, but they are lacking in fire compared with diamond. Sapphire is tough and, among natural stones seen in jewellery, it is second only to diamond in hardness.

A selection of topaz gemstones, including a colourless option (top left). Photograph by Pat Daly.

White opal is not comparable to diamond in the same way as transparent white stones. It is soft, brittle and translucent, but it displays spectral iridescence, which is rare amongst gemstones. It, too, is expensive in its better qualities, and prices can be similar to white sapphire. However, white opal is a true alternative to diamond, since it does not compete with it, but offers a different kind of beauty, displaying flashes of brilliant colour against a subdued background in which brilliance and fire play no part.

In addition to the stones described above, there are about six common white stones and another six, which are rarer but not too hard to obtain in the gem trade and might be added to the list. 

Since alternatives exist, there is no need to restrict the choice to one stone; a collection could be made of those which are easily available. As a point of interest, there is a collection of white gemstones, which was comprehensive at the time it was made, that was donated to Gem-A by David Kent, a well-known gemmologist, teacher and examiner for the Association.

Main image: rough diamond crystal photographed by Henry Mesa.