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.

1770, “I. Earths”, “1. Calcareous”, in Gustav von Engestrom, transl., edited by Emanuel Mendes da Costa, An Essay Towards a System of Mineralogy, London: Printed for Edward and Charles Dilly, translation of original by Axel Fredric Cronstedt, “B. (Sect. XIII) United with the acid of vitriol. Gypſum”, page 22

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.

1771, J. Hill, “Native Fossils”, in Fossils Arranged according to their Obvious Characters; […], London: Printed for R. Baldwin, […]; and P. Elmsly, […], “Class II. Selenite. Selenites”, page 33

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.

1797, “GYPSUM, Plaster-stone, or Alabaſter”, in Encyclopædia Britannica; or, a Dictionary of Arts, Sciences, and Miscellaneous Literature; […], 3rd edition, volume VIII, Edinburgh: Printed for A. Bell and C. Macfarquhar, page 257, column 2

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.

1825, Granville Penn, “Notes”, “IV. On the Numerous Revolutions of M. Cuvier”, in A Comparative Estimate of the Mineral and Mosaical Geologies, 2nd edition, volume II, London: J. Moyes, for James Duncan, page 376

17. Gypsa developed from anhydrites, grey gypsum-bearing limestones with bands of sandstones. The layer is covered with low-angle, turfy talus. Gypsa are white, grey, pink. Sandy limestones are light-grey. 22 m.

1984, Guidebook, International Geological Congress, […], page 84