406 , STUDIES FOR STUDENTS 



for a long" time. Very brittle, being thus distinguished from 

 taenite, with which it is often confounded. Another propert}" 

 which distinguishes it from taenite and from cohenite is that it 

 is insoluble in copper-ammonium chloride. It is soluble in 

 ordinary dilute acids and in acetic acid. Does not reduce cop- 

 per from a copper sulphate solution. Easily fusible before the 

 blowpipe to a magnetic globule. It occurs as crystals, flakes, 

 foliae, grains, and as needles. In the latter form it was long 

 regarded a separate mineral, and was known under the name 

 of rhabdite, but the identity of rhabdite and schreibersite has 

 been proved by Cohen. The needles and plates often exhibit 

 angular outlines. Individual masses of the mineral often reach 

 a considerable size, one from the Carlton iron being 14 '^'". in 

 length. The mineral also forms a considerable portion of the 

 mass of some meteorites, such as Bella Roca, Primitiva, and 

 Tombigbee River. It is the most widely distributed constituent 

 of iron meteorites, aside from nickel iron, and is believed to be 

 usually associated with the latter mineral in the stone meteorites, 

 though its quantity is so small that it has not often been deter- 

 mined. The small percentage of phosphorus usually found in 

 the analysis of stone meteorites is generally referred to this 

 mineral. Schreibersite has been reported in the terrestrial iron 

 of Greenland, but its presence is not proved. Phosphides 

 similar to schreibersite have been made in several ways arti- 

 ficially. The process followed has been essentially to heat iron 

 to a high temperature together with a phosphorus-bearing 

 compound. 



Graphite. — This substance occurs in grains of sufficient size 

 for ready examination only in the meteoric irons. In these it 

 is usually in the form of nodules but sometimes occurs in plates 

 or grains. The nodules often reach considerable size. One 

 nodule taken from the Cosby's Creek iron is as large as an 

 ordinary pear and weighs 92 grams. Even larger ones were 

 found in the Magura iron. Toluca, Cranbourne, Chulafinnee and 

 Mazapil are other irons which contain considerable graphite. 

 Graphite has been estimated to form 1.17 per cent, of the mass of 



