These samples of danburite, CaB2Si2O8, are on display in the Smithsonian Museum of Natural History. The danburite crystal shown is on the order of 4 cm diameter. The gem is 18.5 carats. The origin of this sample is Burma.
Danburite is a silicate which contains calcium and boron.
These danburite crystals are on the order of 1x12 cm and are from Toroku mine, Miyazaki, Japan.
This danburite gem is 26.1 carats and is from Anajanabonoina, Madagascar.
This danburite sample is about 25x25 cm and is from Charcas, San Louis Potosi, Mexico.