346 CHEMICAL EXAMINATION OF MINERALS 



accident towards the end of the experiment, obliged its determination by loss, which gave 

 a percentage of 55*727. The analysis of the mineral, therefore, gives the following per- 

 centage : — 



Aq . . 0-297 



s 



Si0 3 

 Fe 2 3 

 Mo 



38-198 

 2-283 

 3-495 



55727 



100000 



A calculation of the per centage relations of the molybdenum and sulphur, without re- 

 ference to the other ingredients gives, 



S 2 . . 40-668 



Mo . . 59-332 



100,000 



Dana gives the per centage calculated from the formula MoS 2 =sulphur 40-99, and mo- 

 lybdenum 59*01, and Weber in his tables to Rose's analysis, (late edition,) gives for the 

 same calculation, sulphur 41-123, and molybdena 58-877. 



2. Zircon. — Last summer, Mr. Isaac Lea exhibited to the Academy of Natural Sciences, 

 specimens of Zircon imbedded in magnetic iron, which he obtained from a heap of ore at 

 Eckards' iron furnace, and which was said to have come from a locality eight or nine 

 miles from Reading, N. E. of Pricetovvn. I received specimens from Mr. Lea, and also from 

 Dr. Heister, from the same heap. Mr. Geo. M. Keim visited, at my request, the locality 

 from whence the ore was obtained, and sent me specimens, and also a few of the same 

 kind which he found in the Mineral Spring Valley, just outside of Reading. The Zircon 

 occurs in large crystals firmly imbedded in the ore, which are in some instances well 

 terminated, but brittle, and detached with great difficulty from their matrix, to which they 

 adhere with such tenacity, that the impression left in the matrix after detaching them is 

 polished, of vitreous lustre and of the colour of the crystals, as if they had been melted in 

 the ore after their formation. Their planes and angles (as noticed also by Mr. Lea) are 

 rounded oft* in places, as if they had been subjected to an incipient fusion. The largest 

 crystals which I obtained after carefully breaking several pounds of the ore, measured one 

 and a half inches, by one-quarter inch, by three-eighth inch (nearly.) It was distinctly 

 terminated at one end, and showed traces of termination at the other. The usual crystal 

 form was a right prism terminated by corresponding pyramids, the angles of which were 

 frequently modified. The colour, chocolate brown; opaque; lustre, adamantine; planes, 

 as before stated, uneven. One specimen which was too much broken to form certain 

 conclusions, appeared to be part of one of the terminal pyramids. It was highly modified, 

 possessed perfectly sharp edges and glass smooth planes, of adamantine lustre ; was on the 



