GEOLOGY. 829 



ON THE ARTIFICIAL FORMATION OF MINERALS. 



There are a number of minerals with regard to which most mineralogists, 

 geologists, and chemists are of opinion that they can only be formed by crys- 

 tallization from a melted mass. A considerable portion of these minerals are, 

 however, infusible, or, at least, require such a temperature for fusion as can 

 not reasonably be supposed to have been concerned in the formation of the 

 rocks in which they occur. Some of those compounds, on the other hand, 

 may be easily formed by fusion at a moderate temperature. Thus, more than 

 thirty years since, Mitscherlich showed that augite or pyroxene one of the 

 most widely distributed minerals may be formed by melting together silica 

 and various bases of the magnesian series, in such proportions that the oxygen 

 of the acid amounts to twice as much as that of the bases. He also showed 

 that this mineral substance, with its proper form, occurs in the slags obtained 

 in metallurgical operations, and the subsequent examination of slags has led 

 to the recognition hi them of several other compounds identical with, or anal- 

 ogous to native minerals. Nevertheless, there are a great number of minerals 

 in whose origin, it is very probable, intense heat has exercised an essential 

 influence, which have never been produced artificially, nor observed in the 

 products of metallurgical operations. The very happy, and in some respects 

 fertile idea of Ebelmen, to expose substances to the joint influence of heat and 

 a solvent capable of being volatilized, and thus obtain them crystallized, 

 has furnished some very valuable results ; but although boracic acid the solv- 

 ent used has been found in many native minerals, in which its presence 

 had not been suspected, still its occurrence is too rare to admit of the opinion 

 that it has played any very considerable part in the production of the more 

 widely distributed minerals constituting the earth's surface. 



Forchammer has recently made experiments of the same character as 

 those of Ebelmen. but with substances as solvents which are less rare than 

 boracic acid chlorid of sodium, calcium, mangnesium, etc. 



The production of apatite was the object of the first experiments, and he 

 was led to them by the results of his analysis of sea-water, and his observa- 

 tions of the constant presence in it of phosphate of lime, together with a still 

 smaller amoxint of fluorid of calcium. 



After failing in every attempt to produce apatite in the wet way, and 

 guided by the circumstance that apatite occurs chiefly in lava and metamor- 

 phic rocks, under conditions which appear to indicate an igneous origin, he 

 came to the conclusion that if this was the case, chlorid of sodium might 

 have been concerned in its formation. 



By melting phosphate of lime with chlorid of sodium, and allowing the 

 mixture to cool very slowly, a mass was obtained which presented a great 

 number of cavities containing an abundance of long columnar crystals. Tho 

 residue left, after treating this mass with water and then with acetic acid, cor- 

 responded with the composition of apatite. The density of this artificial 

 apatite was found to be 3'069, and the hardness so great that a slab of fluor 

 spar became dull when rubbed with the powder. The occurrence of apatite 



