2S JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 2 



was observed to cut the embedded rhodonite crystals and it may be 

 that the rhodonite is later than and derived from the bementite. Much 

 of the quartz is clearly later than the bementite and in places the 

 bementite is largely replaced by finely crystalHne quartz. Some cal- 

 cite and manganiferous calcite are also later than the bementite, as 

 is also the copper. 



Physical properties. 



The fresh bementite is light gray or grayish brown in color, has a 

 vitreous luster, and is transparent in splinters, but on weathering the 

 color darkens and the material becomes dull and opaque, even in 

 splinters. The mineral has a hardness of about 6 and a specific grav- 

 ity of 3.106. It is tough and has a splintery fracture. It is decom- 

 posed by hot acid, and fuses easily to a black glass. 



Under the microscope the mineral is seen to be in felted aggregates 

 of fibers or plates. Most of it is very finely crystalline but in some 

 parts the crystalhzation is coarse and tends to be spherulitic; tiny 

 veinlets of more coarsely crystalline mineral, with elongation across 

 the walls, cut the finely crystalline material. 



The platy crystals show a perfect cleavage with the acute bisectrix 

 normal to the plates and cleavage. The optical character is - and 

 the elongation is therefore +. The axial angle is near o. The indices 

 of refraction are a = 1.624, /^ — 1-647, 7 — 1-647. 



Composition. 



A sample of several grams of bementite that was separated by 

 heavy solutions from the manganese-bearing rock of the Black and 

 White mine and, as shown by the microscope, contained not more 

 than I per cent of impurities consisting of calcite and rhodonite, 

 was analyzed by Mr. Steiger with the result shown in column i, 

 table I . For the purpose of comparison, analyses of bementite from 

 Franklin Furnace are given in columns 2 and 3 of table i, caryopilite 

 in column 4, and inesite in columns 5 and 6. In table i are given the 

 chemical analyses, in table 2 the molecular ratios, and in table 3 the 

 molecular ratios reduced to 100. 



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



2. Bementite, Franklin Furnace, New Jersey. Analyst, Steiger. 



3. Bementite, Franklin Furnace, New Jeisey. Analyst, Konig. 



4. Caryopilite, Pajsberg, Wermland, »Sweden. Analyst, Hamberg. 



5. Inesite, Dillenberg, Germany. Analyst, Barwald. 



6. Inesite, Pajsberg, Wermland, Sweden. Analyst, Flink. 



