and Properties of' the Manganese Ores. 47 



It would be superfluous to enlarge here on the propriety of 

 considering this as a species of its own, since, besides Mr Mohs, 

 it has likewise been established as such by Messrs Brooke 

 and Phillips,* and by the Abbe Hauy.f Even in the works 

 of the Wernerian school, the pyramidal forms had been long 

 ago described, in reference to the identical specimen from 

 which the above description was derived. Its locality is 

 Ilmenau in Thuringia. Count BournonJ mentions an ore 

 of manganese crystallized in regular octahedrons, having their 

 solid angles replaced by low four-sided pyramids ; a form 

 which might be explained upon the supposition, that the va- 

 riety, Fig. 12, appears in the regular composition represented 

 Fig. 14. ; at least it would be interesting to have these varie- 

 ties compared again with each other. 



III. — Uncleavable Manganese Ore. 



Regular forms and cleavage unknown. Fracture not ob- 

 servable. 



Lustre imperfect metallic. Colour bluish-black and grey- 

 ish-black, passing into dark steel-grey. Streak brownish- 

 black, shining. Opaque. 



Brittle. Hardness = 5.0 ... 6.0. Sp. gr. ~ 4.145, a bo- 

 tryoidal variety. 



Compound Varieties. Reniform, botryoidal, fruticose : 

 composition columnar, impalpable ; fracture flat, conchoidal, 

 even ; in a second composition it is curved lamellar, the faces 

 of composition being smooth, rough or granulated. Massive : 

 composition granular, impalpable, strongly connected ; frac- 

 ture flat, conchoidal, even. 



Observations. 



The specimen analyzed is from the neighbourhood of 

 Schneeberg in Saxony, and agrees perfectly with the pre- 

 ceding description, extracted from the treatise of Mohs. It 

 consists of alternating layers, having more or less lustre, dis- 



* Phillips, 3d Edit. p. 381. 

 t TraiU, -2d Edit. t. iv. p. 264. 

 \ Catalogue, p. 395. 



