Spinel comes in a variety of colours but the relatively rare opaque
black type is only found in a few areas, including Thailand.
It has been
mined in Thailand for centuries, especially in the
amphur
Bo Phloy in the province of
Kanchanaburi,
but also in the amphur Wang Chin in
Phrae
province and the amphur
Sri Satchanalai
in
Sukhothai
province.