Page:Theophrastus - History of Stones - Hill (1774).djvu/310

 Forms of Spar are compoed of Rhombs; and the Contruction of Spar, and of Crytal, are perfectly different, even while their Forms are the ame.

Spar is eldom found original, and free: A few pure Rhombs; and two Columns, double pointed, which were dug in the Hartz Foret; are all I have of it.

Nature has mixed its Particles among the Matter of the Marbles and Limetones; from whence it is wahed forth by the pervading Water, and left lowly by it, in their Cracks and, Fiures; where it aumes thee various Forms:

In this latter Cafe the rude Mas continues uncoloured, and is the Root; and the columnar or pyramidal Figures rife from it frequently yellow, often of other Colours: Thee cut into a Kind of Gems, but till have the double Refraction