Danburite

Danburite is a calcium borosilicate that forms in contact metamorphic environments and in evaporite deposits associated with boron. It was first described in 1839 from Danbury, Connecticut (hence the name), but the world's finest gem-quality crystals come from the Charcas mining district in Mexico.

Mexican danburite crystals are remarkable for their size, clarity, and crystal perfection. Transparent, well-terminated prismatic crystals exceeding 10 centimeters are available - a rare combination of quality and size among collector gemstones. The crystal habit resembles topaz (wedge-shaped terminations) but danburite lacks topaz's perfect cleavage, making it actually more practical for jewelry.

Danburite occupies an interesting market position - it offers diamond-like brilliance and fire in a durable, affordable package, but remains relatively unknown outside collector circles. It's essentially a hidden gem in the literal sense.

Danburite is identified by its prismatic crystal habit with chisel-shaped terminations, hardness of 7, and lack of cleavage (unlike topaz, which it resembles). The vitreous luster and excellent transparency are notable.

Distinguish from topaz (has perfect basal cleavage, higher SG at 3.53), white sapphire (much harder at 9), and quartz (different crystal habit, lower SG). Danburite's specific gravity (3.00) sits between quartz (2.65) and topaz (3.53), which helps in identification.