Scheelate of Iron, or Wolfram
- Wolfram. De Lisle, t. ii. 311. and iii. 262.
- Scheelin ferruginé. Haüy.
This substance had long retained the German name of Wolfram, although mineralogists were much divided about what class to refer it to, until Scheele had discovered Tungsten. It is found in tolerable quantity in Cornwall, and is said to be mostly found in Tin-Countries. We, however, have specimens from the Isle of Man by favour of His Grace the Duke of Athol, and Lord James Murray. I understand that Tin has formerly been known there. Much Spathose Iron Ore has been found there, very much of the same nature and kind as that figured in tab. 63. of this work.
The present specimen was the gift of my good friend P. Rashleigh, Esq., often mentioned in this work, and is of the more consequence as it is in some parts crystallized, so as to allow me to describe the form of its crystals, and in which state it is rarely seen.
The primitive crystal is a cube which may be fractured parallel to one of its faces, commonly with great ease, and parallel to another with some difficulty; but in the direction of the third with much irregularity. The crystals on the upper specimen are so small that they cannot be understood without the help of a lens. It is accordingly represented by an outline on the left hand of the plate to show its modification, and another more complicated on the right. By examining these it will be found that they modify principally on one side of the crystal, leaving the other sometimes unchanged. The right hand one is more compound than any of Haüy’s crystals.
The lower specimen has part of a pyramidal face exposed, and the plated fracture is very distinct as well as the shining lustre of the surface: this somewhat resembles the specimen from the Isle of Man, and is the most usual form of large ones.