Fahlunite Enlarge
[Undated]
Exotic Mineralogy
XC
Silex Fahlunensis

Fahlunite

  • Syn.
    • Fahlunite. Bournon 99.
    • Hard Fahlunite. Hisinger, see Thompson’s Annals of Philosophy, ix. 79.

The name Fahlunite has been applied to the variety of Spinelle called Automalite, by Karsten, and subsequent authors; but English collectors have long- distinguished by that name a mineral from the same place that resembles precious Serpentine, but is foliated: it is generally of a brown colour, yet varieties occur of different shades of green and greenish black. The brown translucent varieties are often crystallized in large hexahedral prisms, in which the foliated structure is perpendicular to the axis ; the crystals are imbedded in a dull grey talcose rock or Potstone, accompanied by Galæna, Copper, and Iron Pyrites. The green varieties are disseminated through a similar rock, but possess less transparency, are more waxy, and shew the foliated fracture less distinctly. The hardness of both varieties is greater than that of Carbonate of Lime, but less than that of Fluor. The surfaces of the laminæ are smooth and shining; the cross fracture presents an uneven dull waxy surface, and is rather splintery; as the colour becomes more intense, the waxy appearance is stronger, the opacity increased, and the hardness diminished. It was first brought to England from Fahlun in Sweden, by Dr. E. D. Clarke.

The analysis of a yellowish brown variety, by Hisinger, gives—

Silica 45.90
Alumine 31.10
Magnesia 13.50
Oxide of Iron 3.00
Oxide of Manganese 0.50
Lime, Zinc 0.20
Volatile matter 3.00
97.20
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