Sulphate of Barytes

Ponderous Spar, as this was commonly called in England, agrees with the Greek term βαρυτης, heavy. The uncommon weight of this substance in comparison to that of other stones has very naturally obtained it this appellation. It is frequent in or near lead or iron mines in many parts of the world, as well as in many places in Great Britain, as Derbyshire, Cumberland, &c.—When transparent, it is generally crystallized and separable into laminæ, much resembling carbonate of lime, and gives a double refraction through the rectangular faces only, but somewhat weaker than that of carbonate of lime. This is a curious substance, and perhaps has not yet been noticed. It may lead to the true nature of double refraction. Haüy ahd recourse to the ingeneous method of forming artifcial faces to discover this property.

Our specimen is on an iron ore from Lancashire, and is as near the primitive as is generally seen in Great Britain.