Gypsa

When a ſmall quantity of any gypſum is melted together with borax, the glaſs becomes colourleſs and tranſparent; but I have found ſome ſorts of alabaſter and ſparry gypſa that, when melted in ſome quantity with borax, yield a fine yellow tranſparent colour, reſembling that of the beſt topaſes.

Source: wiktionary

We find it tranſparent, of various Figures; but compoſed all of united Rhombs: and when its concretion has been interrupted, we ſee it in the forms of granulated, fibrous, or ſcaly maſſes, and call them Gypſa, or Plaiſter Stones.

Source: wiktionary

The Iſle of Sheppey affords a kind of ſpar-like gypſa, of a fibrous nature, and always accreting like the radiations of a ſtar on the ſeptaria, and thence called ſtella ſeptarii.

Source: wiktionary

The gypsum and rock-salt are found also in soils long posterior to the sand-stone with clay.—We have seen, that M. Steffens considers the gypsa of Lower Germany as making part of the chalky formation; and the salt-waters, which issue in that country, are referred to these gypsa and to the salt which they contain.

Source: wiktionary