Ridden and Mackintosh — Thorium Mineral. 461 



Art. XLYIII. — On a new Thorium Mineral, Auerlite / by 

 W. E. Hidden and J. B. Mackintosh. 



While one of us was about completing a contract for twenty- 

 six tons of zircons, to supply a recent large demand for that 

 mineral, several crystals of the mineral forming the subject of 

 this paper were noticed in the very last shipments from the 

 mine. As the quantity then found was insufficient for a com- 

 plete chemical and physical examination, the locality was re- 

 visited in July last and for five weeks a systematic and laborious 

 search for the mineral in situ was carried on. We had already 

 proved it to be a hydrous mineral rich in thoria, with silica and, 

 strangely, a very appreciable quantity of phosphoric acid. Our 

 interest was centered upon its apparent anomalous composition 

 and a series of careful analyses was made by one of us as soon 

 as the necessary material was procured. As the result of the 

 search at the locality not quite 100 grams were found and it 

 became necessary to mine over 200 kilos of zircons to get even 

 this small amount- 

 It has thus far been found at only two places in Henderson 

 County, North Carolina, namely, at the well-known Freeman 

 mine, on Green River, and on the Price land, three miles 

 southwesterly. At both places it occurs in disintegrated gran- 

 itic and gneissic rocks intimately associated with crystals of 

 zircons, and it is often seen implanted upon them — as a second 

 or after-growth — in parallel position. 



The color on a fractured surface ranges in different crystals 

 from a pale leinon-yedow through various shades of orange to 

 a deep brown-red. The form is distinctly tetragonal, only the 

 unit pyramid and prism being observed, and excepting a ten- 

 dency to a longer prismatic development, it is much like the 

 common type of zircon found throughout the region. The 

 faces being very rough and uneven, no constant angles could 

 be obtained on any of the material, but they closely approxi- 

 mate to those of zircon. 



Fragments of the mineral resemble some varieties of gum- 

 mite and deweylite, but have a more waxy or rosin like appear- 

 ance. It is sub-translucent to opaque, and has a dull yellowish 

 white exterior. It is very brittle and easily crumbled. The 

 hardness varies from 2*5 to 3, some crystals barely scratching 

 cleavage surfaces of calcite. The specific gravity has a wide 

 range, i. e. from 4422 to 4 f 766, the dark- orange-red crystals 

 having the highest density.* 



*S<>me of the crystals were much lighter in color, softer and of specific gravity 

 from 3 7 to 3 - 8. These we propose to examine and report upon later. 



Am. Jour. Sci.— Third Series, Yol. XXXYI, No. 216.— Dec, 1888. 

 29 



