Chanthaburi Province is situated in the northeastern coastal belt of the Siam Gulf. It borders with Trat Province
. The combined area is sometimes referred to as the Chanthaburi-Trat gem region.
This rich gem region, which produces about 90% of the Thai rubies and sapphires, as well as some zircons, is in southeastern Thailand on the western slopes of the Dangrek Range, near the boundary with Cambodia
. In 1850 corundum
was first discovered in the cone-like top of what became "Gem Mountain" in Khao Ploi Waen
, 8 km SE of Chanthaburi. The Pailin
corundum-bearing field in Cambodia
borders this region.
The deposits are dominantly alluvial placers derived from the weathered underlying basalts. Eluvial residual placer deposits have been reported.
from Chanthaburi are usually rounded, prismatic crystals with an average size of 3 to 6 mm. Opaque crystals may have a length up to 10 cm. Light blue and blue sapphires prevail, bluish-green, green and yellow stones are less common.
Ref: E.Ya. Kievlenko (2003) Geology of gems, pp. 44, 66
Gem list contains entries from all listed localities in region.
Localities in this Region