256 ON THE OCCURRENCE OF WOOD-TIN ORE. 
able width ; and these—even when no thicker than paper—dis- 
play the most capricious and complicated flexures, and still preserve 
a fibrous structure. Both in the broader parts of these narrow 
veins, and in the small bodies of ore, whether imbedded in ordi- 
nary cassiterite or in earthy ingredients, radiated-crystalline,—as 
well as a concentric lamellar-structure prevails, the successive 
rings or cylinders of ore being alternately of clove-brown, and of 
brownish yellow, hue.* These aggregations of divergent crystals 
sometimes enclose kernels of ordinary tin-ore; but now and then 
they radiate from minute cavities (vughs), which—in such cases 
are lined with microscopic pyramids of cassiterite. 
As wood-tin-ore has been so rarely found in Jlodes, and in no 
case, yet recorded, from so great a depth as in Wheal Vor, I 
venture to hope that the foregoing description of the conditions 
under which it occurred, may not be uninteresting. One of the 
best specimens of wood-tin-ore yet obtained here accompanies this 
memorandum, and I shall be gratified to find that it has been 
found worthy of a place in the Museum of The Royal Institution of 
Cornwall. 
Wheal Vor, 23rd April, 1873. 
* Phillips, W. J., Introduction to Mineralogy, (Third edition), p. 253. 
