THE 



AMERICAN JOURNALOFSCIENCE 



[FOURTH SERIES.] 



Art. XII. — The Role of Water in Tremolite and Certain 

 Other Minerals ; by E. T. Allen and J. K. Clement. 



Object of the Investigation. — A study of the composition of 

 tremolite was undertaken with several objects in view. In the 

 first place, it belongs to the series of calcium and magnesium 

 metasilicates, all the other known members of which have 

 already been studied in this laboratory. Secondly, it is the 

 simplest known amphibole with the exception of kupfferite, 

 and consequently affords an advantageous opportunity for 

 further study of the relations .which exist between the amphi- 

 boles and the pyroxenes. For a complete investigation of this 

 kind, pure minerals are necessary, and since natural minerals 

 can rarely be classed as such, we sought to prepare tremolite 

 synthetically. But, the ordinary methods proving inadequate 

 to the task, we proceeded to a study of the natural mineral, in 

 order that we might find out what elements were really essen- 

 tial to it, as well as what physical conditions were necessary to 

 its existence. 



One of the most important questions which presented itself 

 in this connection was whether the mineral must be synthe- 

 sized by wet or dry methods ; whether it was hydrous or an- 

 hydrous. Some preliminary work which we had done proved 

 that it was incapable of existence above about 1000°-1100°, a 

 temperature at which it is still in the solid state. Attempts to 

 form it by heating a glass of the same composition below this 

 temperature, or by rapid cooling of the melt, failed, indicating 

 not only that the natural mineral must have been formed from 

 solution, a conclusion in accord with geological evidence, but 

 further, that it could be obtained in no other way. At first, 

 molten salts were tried as solvents, on account of the difficulty 

 of working with water at temperatures much above the 



Am. Jour. Sci.— Fourth Series, Vol. XXVI, No. 152.— August, 1908. 

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