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Forms of Spar are compoſed of Rhombs; and the Conſtruction of Spar, and of Cryſtal, are perfectly different, even while their Forms are the ſame.
Spar is ſeldom found original, and free: A few pure Rhombs; and two Columns, double pointed, which were dug in the Hartz Foreſt; are all I have of it.
Nature has mixed its Particles among the Matter of the Marbles and Limeſtones; from whence it is waſhed forth by the pervading Water, and left ſlowly by it, in their Cracks and, Fiſſures; where it aſſumes theſe various Forms:
1. Pure Rhombs of a larger Size.
2. Rude Maſſes, formed of coarſe connected Rhombs.
3. Plates compoſed of connected Rhombs.
4. Columnar, Pyramidial, and Cubic Figures, fixed upon the Surface of theſe rude Maſſes[1].
In this latter Cafe the rude Maſs continues uncoloured, and is the Root; and the columnar or pyramidal Figures rife from it frequently yellow, often of other Colours: Theſe cut into a Kind of Gems, but ſtill have the double
- ↑ The Stone from which the Swediſh Acid: before deſcribed is obtained, has been added to theſe; but erroneouſly. It is a diſtinct Body.
Refraction
