Magnesian Sulphate of Soda
In British Mineralogy I have had the pleasure of giving the figure and locality of the Satin Spar, which is likely to be lost to posterity except in the figure. This salt, with a so singularly beautiful satiny lustre, puts me in mind of it;—how far it may be permanently preserved I do not know; it however is likely to be possessed but by few except in the figure; we are therefore thankful for an opportunity of publishing it by favour of Mr. Heüland, in whose valuable collection the specimen is to be placed. It is from Calatayud in Arragon.
The same salt is found crystallized in flat six-sided prisms, and as a mealy efflorescence of a snow-white and yellowish white, in the country around Sedlitz and Saidschutz, and also at Pilln near Brün, and named Reussite. See Jameson’s Syst. of Mineralogy, ed. 2. Vol. I. p. 319.