Exploring Guyana’s semi-precious stone resources

Guyana possesses significant semiprecious stone resources of jasper, amethyst, agate, black pearl and green quartz. As the Guyana Geology and Mines Commission (GGMC) has shown over the years, our semiprecious stone resources have excellent potential for supporting lapidary manufacturers of jewellery, cabochons and artefacts. Even though they present excellent economic prospects for the creative entrepreneur, these resources remain under-utilized.

GGMC has resolutely promoted the development of lapidary manufacture, based on our semi-precious stone resources. Such promotional support has extended from mapping and quantification of geological resources to the establishment of a lapidary, and training staff in different aspects of creating cabochons and artefacts from semi-precious stones.

Jasper from Roraima plateau
Jasper is impure, opaque form quartz, belonging to the chalcedony group of compact silica minerals composed of minute crystals of quartz with sub-microscopic pores. Impurities of iron oxide and iron hydroxide impact its characteristic red, brown, cream, yellow, grey or green colouration. Jasper is very hard and takes high polish, and is used widely as an ornamental stone.
The Lapidary Workshop of the GGMC produces distinctive cabochons (a gemstone that has been shaped and polished as opposed to faceted) and artefacts: paper weights, desk bowls, ash trays and clock faces – from the wide variety of jaspers obtained from massive deposits in the Roraima group of sediments, where the river network of the upper Mazaruni River basin has cut deeply into the late Precambrian Roraima group of sediments, exposing intercalations of jasper.
Deposits containing more than 15 million tons of bedded jasper and chert are found within a ten mile radius of Orinduik, Kurukabaru and Kato villages, which are connected by walking trails. Jaspers found in these areas are red, grey, dark brown, cream, mottled, spotted dark brown/cream and banded dark brown/grey, but the deep red variety is the most common. Occurrences of the green jasper are confined to the upper reaches of the Kato River, a left bank tributary of the upper Mazaruni River.

Amethyst from South Rupununi
Amethyst is a variety of purple or bluish-violet quartz that exhibit varying depth of colour. The name ‘amethyst’ comes from the Greek word ‘amethustos’ meaning “not-drunken” which was originally given on account of the curious but mistaken belief that the wearer became immune from the effects of drinking potent liquors. Its purple colour, due to iron impurities (possibly in conjunction with natural radioactivity), its transparency and vitreous lustre make this mineral suitable for use as a gemstone.

Banded and fire agate
Deposits of banded and fire agate occur in the North Rupununi savannahs in the southwest of Guyana. The best deposits are found in Bon Millee on an old terrace of the left bank of the Ireng River in the North Rupununi savannahs, approximately 31 miles north of Lethem and in a gravel bed deposit at Sishwa, 4 miles down the Ireng River from Bon Millee.
The Lapidary Workshop of the Guyana Geology and Mines Commission leads the way in producing attractive cabochons, paper weights and clocks of banded and fire agate from the Rupununi. The agates are associated with well-rounded but unsorted quartz sand, pebbles and cobbles.

Black pearls from Aranka, Upper Cuyuni
At the Lapidary Workshop of the Guyana Geology and Mines Commission, they tumble and polish unique brown concretionary, ferruginous nodules from Aranka to produce ‘Black Pearl’ beads of high quality, famed for their roundness, high lustre and the eye-catching silver jewellery creations they produce when set in rings, earrings, pendants and much more. Black pearl beads can be drilled and strung or pasted on to jewellery mounts. These pearls are easily recovered from enclosing Aranka clay by simply sieving and washing.
Although the black pearls are reported in several other countries, Aranka black pearls are known to be the best quality. The legend associated with black pearls is that the original male Amerindian inhabitants of Guyana wore them to enhance their masculinity. Not surprisingly, the legend goes, the Amerindian women ensured that their men always carried at least one black pearl in their possession.

Green quartz from the South Rupununi
At the Lapidary Workshop of the Guyana Geology and Mines Commission, an unusual sea-green variety of quartz from a residual deposit approximately 8km west North West of Aishalton is used to produce cabochons, paper weights and clocks. It is thought that the striking green colour is due to copper impurities in the quartz. Green quartz is especially appealing when set in gold, gold-plated, or costume jewellery.
Geologist Karen Livan, manager of the environmental division of the GGMC, said concerning the potential of developing these semiprecious stones, “We concede that we have just touched the tip of the iceberg. There remains largely untapped, good potential for the production of artefacts and jewellery of these stones. Resources are substantial, possibilities are many.” (Text by Geologist Karen Livan)