JAN. H>, 1921 PARDEE, LARSEN, & STEIGER! BEMENTITE 31 



dices of refraction of the caryopilite are not sufficient to cast any- 

 serious doubt on the identity of the two minerals. The name bemen- 

 tite has the priority, and should be retained for the species. 



The composition of the inesite and ectropite is much like that of 

 bementite, but their other properties are sufficiently different to dis- 

 tinguish them. 



NEOTOCITE. 



Occurrence and properties. 



The neotocite is present in small veinlets cutting the bementite. It 

 is brown to black, has a clear, resinous luster, and a cpnchoidal frac- 

 ture. It is brittle and has a hardness of about 4. Under the micro- 

 scope it is clear red-brown in transmitted light, isotropic, and has an 

 index of refraction varying from 1.45 to 1.50 and averaging about 

 1.47. For comparison, neotocite from vSweden was examined. It is 

 black, has a conchoidal fracture, and a vitreous luster and looks like 

 coal. It is brown in powder and in transmitted light under the 

 microscope is clear brown. In part it is isotropic with an index of 

 refraction varying from 1.53 to 1.56, in part it is birefractory with a 

 mean index of refraction varying from 1.54 to 1.58 and a birefringence 

 of about 0.02. The birefractory part is clearly crystallized from the 

 amorphous part and its variable properties are probably due to 

 incomplete crystallization giving submicroscopic admixed amorphous 

 material. The crystalline part is probably bementite. The name 

 neotocite should be confined to the amorphous mineral having the 

 approximate chemical composition MnO.vSiO2.wH2O while bementite 

 should be applied to the crystalline mineral (8 MnO.7 SiO^-S HoO). 

 In common with most amorphous minerals, the composition of neo- 

 tocite is much less uniform than is that of the crvstalline form, be- 

 mentite. 



Composition . 



A chemical analysis made of powder separated from admixed quartz 

 and calcite by heavy solution and carrying a small amount of impur- 

 ities is shown in tables 5 and 6. 



1. Neotocite, Olympic Range, Washington. Analyst, Steiger. 

 2 and 3. Neotocite, Gestrickland. Analysts, Cleve and Nordenskiold. 

 4 and 5. Stratopeite, Pajsberg. Analysts, Cleve and Nordenskiold. 

 6. Hydrated manganese silicate, near neotocite, from Dillenberg mining 

 region, Germany, described by A. Schneider.'' 



The mineral dissolves readily in i : i hydrochloric acid with sep- 



^ Jahrb. Preuss. Landesanstalt, 472 et seq. 1887. 



