203 DESCRIPTION AND ANALYSIS 



this mineral to Mr. Jefferson ; I have readily assent- 

 ed to this proposal, and we now offer this mineral to 

 the public under the name of the Jeffersonite. 

 This mineral has hitherto been found in too small a 

 quantity, to offer any utility in the arts. Should it, 

 however, be found in sufficient abundance, it would 

 become valuable as a flux for the iron- works in the 

 vicinity. The absence of magnesia, and the abundance 

 of manganese, seem to make it very valuable for this 

 object. 



REMARKS. 



The Jeffersonite presents some points of resem- 

 blance with the Pyroxene of Haiiy, but still it can 

 be well distinguished from it. Its cleavages are es- 

 sentially different from those of the Pyroxene, but 

 appear to approach some of the faces of crystals of 

 substances which have been united to this species : 

 for instance, the augles in the Diopside (Mussite and 

 Alalite), Fassaite, and in the Pyroxene analogique, 

 come very near some of the angles of cleavage ob- 

 tained in the Jeffersonite. I at first indulged the 

 idea, that these cleavages might be considered as 

 cleavages parallel to the faces of secondary crystals 

 of Pyroxene, but upon reflection I am fully convinc- 

 ed that this is not the case; for the angles which 

 we have measured, cannot be deduced from the others 

 by a strict mathematical calculation, and though they 

 may approximate, they are not the same. Besides, 

 no analogy can warrant us in admitting, that the re- 

 gular cleavages of one substance can disappear en- 



