284 MINERALOGY 



ing organic matter, through which the magma, while still in a fused 

 condition, was forced. In most cases this magma has been basic, 

 containing large quantities of magnesium silicates. After solidi- 

 fication they are of the nature of peridotites. 



Artificial diamonds were produced by Moissan, by dissolving 

 carbon in fused iron ; upon cooling the fusion quickly in melted 

 lead, the outer portions solidify first and the resulting contraction 

 subjects the still liquid interior to enormous pressure. Under 

 these conditions the excess carbon was separated as small diamonds. 

 If the fusion was cooled slowly and without pressure, the more stable 

 crystalline form of carbon, graphite, was formed. The diamonds 

 contained in meteors, as the Canon Diablo specimens, must be of 

 this nature. Diamonds were also produced by J. Friedlander, 

 who dissolved graphite in fused olivine ; from these experiments 

 it was found that fused magnesium and calcium silicates dis- 

 solved carbon and favored its separation on cooling in the form of 

 diamond, a condition very similar to that of the natural deposits. 



GRAPHITE 



Graphite. Carbon, Black Lead, Plumbago ; C ; Hexagonal ; 

 Type, Dihexagonal Alternating; c = 1.3859; 0001 A lOll = 

 58, r A r' = 94 31' ; Common forms, c (0001), r (1011) ; Cleavage 

 basal, perfect ; Laminae, pliable ; H. = 1-2 ; G. = 2-2.3 ; Color, 

 black to steel-gray ; Streak, gray to black ; Luster, metallic to dull 

 and earthy; Opaque, feels greasy and marks paper. 



B.B. Infusible, deflagrates on coal when mixed with nitre 

 and heated to a high temperature. Insoluble in acids. 



General description. Occurs when crystalline in thin tabular 

 crystals flattened parallel to the base, often in foliated masses, 

 radiated scaly, compact or earthy. Many specimens are impure 

 from oxides of iron, clay, or mixture with sand. 



Cliftonite is an isometric form, harder than graphite, contained 

 in a meteoric iron from Australia and also from Cooke County, 

 Tennessee ; these crystals have been regarded as pseudomorphs after 

 diamond. 



Graphite is very common in crystalline schists, as in the Adiron- 

 dacks and at Ticonderoga, New York, and High Bridge, New Jersey, 

 where it has been formed from the organic matter, contained in the . 

 original sedimentary deposits, by the metamorphic action of heat 





