NO. 2145. NOTES ON ALl'NITE, PSILOMELANTTE, ETC.— WHERRY 



85 



PHYSICAL PROPERTIES. 



Color : Black with slight bluish hue ; streak brownish-black. 



Luster : Dull-submetallic ; more brilliant against surfaces of quartz ; 



opaque. 

 Structure: The several types exhibited by colloid minerals — botry- 



oidal, globular, compact, and dendritic ; fracture uneven. 

 Hardness : Varying from 3 to 5^. 

 Density : Varying from 4.20 to 4.30. 

 Optical properties: Indeterminate. 



Indeterminate. 



CR\'STALLOGRAPHIC PROPERTIES. 



CHEMICAL PROPERTIES. 



Qualitative tests : Before the blowpipe gives reactions for Mn and Li 

 (flame red !). Soluble in HCl, with evolution of CI; solution gives 

 reactions for Mn, Fe, Al, Co, and SiOo and traces of other elements. 



Quantitative composition : The most homogeneous material obtain- 

 able from the specimens was submitted to Dr. J. E. Whitfield, of 

 Booth, Garrett, and Blair, who obtained the results given below 

 (with the exception of the Li,0, which was determined by the 

 writer, using the spectroscopic method) : 



The results of analysis of psilomelanites (the termination ite is 

 added for uniformity) have been previously interpreted in various 

 ways. Rammelsberg^ regarded the barium, manganous manganese, 

 etc., as united with manganic manganese to form manganites, of the 

 formula M"" (MnOg)". Laspeyres^ considered that these elements 

 are present as basic manganates, M"oO(Mn04)'', and his view was 

 adopted by Dana.^ In the light of colloid-chemistry the mineral 

 might be interpreted as colloidal manganese dioxide containing ad- 

 sorbed substances. 



1 Handworterbuch chem. Theils Mineralogie, 1841. 

 2Joum. prakt. Chem., vol. 13, 1876, pp. 1 and 215. 

 3 System of Mineralogy, 1892, p. 257. 



