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Selenitesy (have been frequently called 

 Lapides Specidares) the Moon-ftone is of a 

 brighter Colour than the Spar, and is ta- 

 bulated, or can be feperated into thin 

 Plates the Selenites do not ferment with 

 acids, but readily calcine in theFire they 

 confift of feveral Species, and are found 

 in many Parts of the World, in England^ 

 in the Clay-pits in Stafford/Jiire^ and par- 

 ticularly many of them in a bluifh Clay 

 near Harhorough in OxfcrdJJiire, It has 

 been faid that the Chinefe Moon-ftone fuf- 

 fers Increafe and Diminution in Sympathy 

 with the Increafe and Decreafe of the 

 iVIoon. 



Gypfum IS of this Kind, but lefs tran- 

 fparent, and more eafily calcined, yield- 

 ing a fine white Powder, of which is 

 made Plaifter of Paris^ a -Commodity 

 well known. The Gypfum has fomething 

 the appearance of the fofter Marbles, 

 bright, gloffy, and in a fmall Degree 

 tranfparent ; it does not give Fire with 

 Steel, nor ferments v/ith or is diflbluble 



in 



