An Account of Certain Perfect Minute Crystal Stones, by J. Parsons, M. D. & F. R. S.

XVIII. An Account of certain perfect minute Crystal Stones, by J. Parsons, M. D. & F. R. S. Read June 27. THE Drawing here annexed, Tab. III. 1745. Fig. 10. represents a small Crystal magnified; it is one of a great Number brought by a very curious Gentleman from Gibraltar, who has caused many of them to be set in Buckles of different Kinds, for the Wear of his Lady and himself: And altho' they are formed and polish'd by Nature; yet they look very bright, and produce a very good Effect in the Buckles. They were found accidentally. This Gentleman saw a Man cleaving a Rock near that Town, and observ'd a great Quantity of fine black Powder fall from its Crevices; and, being very curious, he examined the Powder, and found these little Stones in Clusters, consisting of no more than twelve or fourteen each; and each Cluster lying at considerable Distances from one another. They are all of the same Form, some less perfect than others, and are in general Hexagonals. XIX. A Letter from Mr. John Ellicot, F. R. S. to the President, concerning the specific Gravity of Diamonds. Read July 4. AS, from some Experiments I have lately had the Opportunity of making, it appears highly probable, that what has formerly