South of Khao Ploi Waen
, near the village of Bang Kha Cha, blue, bluish green and yellow sapphires
are extracted from marine beach placers in silty lowlands in the tidal zone of the Gulf of Thailand.
Dark gray ("black") star sapphires
are of special interest.
Ref: E.Ya. Kievlenko, Geology of gems, 2003, p. 66