Page:Theophrastus - History of Stones - Hill (1774).djvu/97

, aumed into it at the Time of its original Formation, as in the other Gems; and is thence yellowih, reddih, or bluih, and ometimes, but very rarely, greenih. As the Diamond thus is ometimes of the Colour of other Gems, but greatly uperior in Hardnes to them; o the common Crytal, ometimes, from the ame Accidents, reembles them, and is much ofter, and of little Value. Crytals thus tinged are what the Jewellers call Batard Emeralds, Sapphires, &c.

The Diamond is compofed of various Laminæ laid cloe one on another; and Jewellers of Skill will ometimes find the Joinings, and with the Edge of a fine Intrument plit a Diamond into two of equal apparent Surfaces.

If the plain Surfaces of the Plates of a Diamond be turned to the Focus of the tronget Burning-glas, it receives no Hurt, even by that powerful Fire; but if the Edges and Joinings of the Laminæ are turned to it, the Stone eparates at them, is reduced into a number of Scales or thin Flakes; and lot.

The Form of the Brazil Diamond differs from the Oriental, as well as do its Qualities. There are Shirly, or Baaltine, reemblances of all the Oriental Gems; and this is uch of the Diamond; and no other. De Laet was acquainted with it, and with its qualities. Agricola knew its Dodecahedral form. Wallerius accurately decribes its Faces by their cubic Shape. The Bravil Diamond has the ame Electric, and the ame Phophoric Properties, with the Oriental: After it has been held in the Sun, it has a ilvery Brightnes in the dark; and the ame Quality, in ome Degree, when rubbed: and it takes the Foil, as the Oriental Diamond. But they all want the perfect Hardnes of the Oriental Diamond; and they have omewhat les pecific gravity; and they can be melted by the extream force of Fire, which the Oriental Diamond cannot.

We are not to expect all Diamonds in their perfect crytalized form; we ee them rounded in the Manner of the pebble Crytals, and like all other crytalized Stones, they vary in the Number of the Angles, even in the ame Species.

Like all the other crytalline Stones, this is alo liable to be tinged to all Colours; but thee Tinges it receives in o mall a Quantity, and in a Degree o delicate, that it is a Doubt XXXIII. The Power thee Stones have of reiting the Force of Fire; is not from the ame Caue with that of