Sangu garnet deposit, Muchinga Province, Zambiai

Regional Level Types
Sangu garnet deposit	Diggings
Muchinga Province	Province
Zambia	Country

The Sangu garnet deposit is located approximately 57 km northwest of the town of Lundazi. It is accessible by the main road from Lundazi, 32 km to Chama, and further another 65 km by left crossing track in the direction to Chasefu School and the village of Chikwa. The undulating terrain in the environs of the garnet deposit is covered by fairly thick bush vegetation and lies east of the Luangwa Valley Game Reserve (north).

The garnet deposit has been worked and then abandoned several times in the past due to the lack of financial resources and limited market. Local miners worked the mine on a small scale, using only hammers, chisels and shovels. Since the time of greatest activity in 2000, about 50 people are involved in mining. The mine is opened by a system of pits arranged in a line, which follows the plagioclase-garnet segregation veins. The exploited near-surface part of mafic granulite is moderately or weakly weathered allowing the use of shovels and chisels. Deeper parts of the exposed garnet accumulations are worked by drilling and blasting, and the extracted material is sorted by handpicking.

Gem-quality garnet at the Sangu deposit occurs in plagioclase segregation veins confined to mafic granulite, as nodular crystals up to 10 cm in diameter. The colour is commonly red to brownish red in transmitted light, with a moderate brown hue. Sangu garnet is pyrope-almandine with 46–47 mol% Prp, 39–40 mol% Alm, 9–10 mol% Grs, 2–3 mol% Adr, and 0.10 wt% TiO2. This garnet is characterised by the presence of abundant acicular rutile crystals. Mine production primarily consists of fractured pieces 1–3 cm in size, 0.5–2 grams in weight.

The Sangu area in Eastern Province hosts the only known commercial deposit of gem garnet in Zambia. In the early 1990s, transparent and facetable, gem-quality garnet of brownish red colour first appeared on the market in Lundazi, and the rough was transported out of Zambia. However, the notable commercial production was not being recorded before 2000. The deposit represents an interesting type of garnet mineralisation, where large gem material occurs in plagioclase segregation veins confined to basic granulites. Petrology of the host rock, mineralogy, and gemmology of garnet from Sangu deposit have not been previously studied.

Other Regions, Features and Areas containing this locality

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