SALMON — MINERALOGICAL NOTES. 
63 
tin-stone or tin-ore), the former mineral is made, in the Profcsor's 
reasoning, a kind of middle term to prove the isomorpliism of its in- 
dividual components (silicic acid and zirconic acid), with stannic acid. 
Ho considers, in fact, that silicic acid may fairly be considered to be 
already found in the form of cassiterite, in zircon ; and believes it 
would not be a matter for surprise to find stannic acid in the form of 
quartz. 
Dr. Genth's paper, in the September number of the " American 
Journal of Science and Arts," on the " OccuiTence of Gold" is very 
suggestive. After the mass of vague verbiage with which we have 
been inflicted on this topic, it is really refreshing to find a man who, 
whether right or wrong, is at least possessed of a definite and com- 
prehensible idea. 
Dr. Genth maintains that the gold found in veins and alluvial de- 
posits has been carried there in a state of solution ; and he brings the 
following instances to prove that, in those cases at least, such must 
have been the case. If these are accurately stated, of which there 
seems every internal evidence, this certainly cannot be questioned : — 
" a, Specimen from Whitehall, Spotsylvania co., Va., shows gold 
associated with tetradymite [telluride of bismuth], hmonite [hydrous 
per-oxide of ii'on], and quartz. The gold is ciystallized in forms be- 
longing to the rhombohedi'al system, and showing very distinctly one 
rhombohedron, scalenohedron and basal plan ;* it is coating tetra- 
dymite, and is evidently a pseudomorph of it. 
" h, The tetradymite of the Tellurium Mine, Fluvanna co., Va., 
and the native bismuth from the peak of the Sorato, in BoHvia, are 
frequently interlaminated vnth gold. 
" c, In the upper portion of the ore-bed in the metamorphic slates 
at Springfield, Carrol co., Md., which near the surface consists of 
magnetite [magnetic proto-per-oxide of iron], and at a greater depth 
of chalcopyrite [copper pyrites] and other ores, fibns of native gold 
have sometimes been observed coating the cleavage-planes of the 
magnetite. On close examination it can be perceived that below the 
film of gold the magnetite is oxidized into hydrated sesquioxide of 
iron." 
In attempting to establish an hypothesis of this kind, the greatest 
* These are the crystalline forms of tetradymite. 
