Thailand.12, Nong Bon, Chanthaburi, gems

Moreau gives a first-hand account of a visit to the Nong Bon ruby mine, about 60 km from Chanthaburi and close to the Cambodian frontier. The deposit was worked by removing roughly 20 m of overburden to reach a gem-bearing alluvial layer about 1 m thick; powerful pumps and water jets broke up the material, after which the lighter fraction was washed away and the heavier gem-bearing concentrate collected and hand-sorted. Daily production was irregular, estimated at 1,000–2,000 carats, but only about 300 carats were considered gem material, including perhaps 2–3 carat stones; associated minerals included black opaque spinels, ilmenite, and black corundum. The rough ruby was generally sold not at the mine but at Bor Rai, where miners and dealers negotiated prices in a busy market. Photographs document the mine, hydraulic working, hand sorting, and trading, while a photomicrograph shows faceted inclusions in a Thai ruby.