Scheelate of Iron, or Wolfram
- Wolfram. De Lisle, t. ii. 311. and iii. 262.
- Scheelin ferruginé. Haüy.
The rarity of this substance in determined crystals, especially in Great Britain, is a sufficient excuse for figuring a specimen of the present appearance, which has no pretension at first sight to value. Experience, however, has shown us that in some things that rarely crystallize a characteristic specimen is a tolerable prize. The present has some small but determined crystals when examined carefully with a lens, and the little middle figure is a singular formation of hexangular plates, which being deposited at the lower part regularly in equal-sized plates, form an hexaëdral column. Those immediately above the column, diminishing by degrees, form part of a pyramid; and a few plates of a little larger dimensions, hanging slightly over at the apex, seem to explain by this small irregularity, that the plates formed before they were deposited. The lower middle outline explains the primitive rectangular figure, and the accumulation on the sides, forming the hexaedral plates. The right hand geometrical figure shows the rectangular primitive or cubic form within the column, which by a little thought may by a tyro be comprehended as the primitive form that accumulates to that of the left hand figure. The hexangular column has four angles of 121° and two of 118°. The gangue is composed of Chlorite, Quartz, Oxide of Tin, and Arsenical Iron, or Mispickel. The specimen comes from Cornwall.
Tungstate of Iron has not, that I know of, been found otherwise than crystallized, although the crystals are almost always interrupted. It may be known from most other substances by its peculiar fracture, which in the tabular crystals is perpendicular to their larger faces. It may be scraped by a knife, giving a chocolate brown powder.