Sulphate of Lime; var. plumose

The upper figure is a curious variety of sulphate of lime, or gypsum, from Matlock. it should seem that sulphur of iron or pyrites, by exposure to damp, decomposes; the sulphur combining with oxygen forms sulphuric acid, which comes in contact with the lime in the rock, and so forming gypsum, oozes out in these fanciful forms; or, in other words, readily produces gypsum more or less crystallized. It is continually forming in many parts of England. Lord Altamont obligingly sent me some nodules of pyrites, in which gypsum is formed, from a well just dug in Cambridge. It is continually crystallizing from the sulphur of pyrites and oyster shells at Shotover Hill, near Oxford.

The lower figure is on a piece of limestone with a fœtid odour, called stinkstone, the gypsum spreading in a very peculiar manner on the surfaces in patches. I was favoured with this from the neighbourhood of Durham, by the Rev. John Harriman.