1 76 Williamshurgh Mineral. 



as a phosphate of lime, and from Mr. Dwight that it is dis- 

 solved by the acids ;* I then for the first time, endeavoured to 

 impress it with a knife, and found to my surprise, that all the 

 varieties were impressed by steel, with little more difficulty 

 than fluor spar. 



I relate the circumstance in order to show the necessity of 

 caution, in drawing conclusions especially from the relative 

 hardness of minerals,/or a softer substance, may, by continued 

 rubbing and grinding be made to impress a harder. Instances 

 of this kind are numerous in the arts, and in the case of the 

 gritty powders used in polishing hard stones. Ropes will 

 wear wood and even stone ; wood will wear metals, and 

 metals will abrade earthy minerals; even a soft leather strap 

 polishes and sharpens the hardest steel. 



I am disposed to think with Mr. Nuttall, that the Williams- 

 burgh mineral is a phosphate of lime, and as it phospho- 

 resces, we must assign it to the variety apatite. This is not 

 the first time that this mineral (strongly resembling several of 

 the gems) has held mineralogists in doubt, as to its nature, 

 and thus justified its Greek name o{ the deceiver.^ 



We add an extract of a letter from Mr. Dwight, dated June 

 1, 1824, prefacing it with the remark, that the minerals men- 

 tioned by him, are all well characterized, and the plumose 

 mica, and the micaceous iron (especially the latter) extremely 

 beautiful. 



" I take the hberty to send you a box of minerals contain- 

 ing the following specimens. 



1. Argentine, Williamsburgh, 



2. Pseudomorphous quartz, do. 



3. Epidote, do. 



4. Plumose mica, do. 



5. Micaceous oxide of iron, Hawley. 



We have recently discovered the locality of argentine. It 

 occurs in large masses of a superior quality — I think some 

 pure masses will weigh tons. 



The quartz is found in the vicinity of the argentine. The 

 dog-tooth projections appear to have formed upon the dog- 

 tooth spar originally. Some of these projections however are 

 rectangular ; perhaps these were formed upon crystals of sul- 



* A fact which I have siace confirmed by experiment, and the dissolved 

 mineral was again precipitated by caustic potash, 

 t From 'AsratTa'ai, to deceive. 



