Outlines of mineralogy / by J. Kidd.

  • Kidd, John, 1775-1851.
Date:
1809
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of mineralogy / by J. Kidd. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    SILEX. The term silex, as applied to a simple earth, is deri- ved probablyfrom those hard pebbles, which are com- monly met with in every part of the world ; and which possess the leading characters of the n. tural compounds of this earth : these are, a degree of hardness sufficient to strike hre with steel; infu- sibility in the fire, when uncombined with other earths ; and insolubility in acids. In Wallerius, and the earlier mineralogists, sihceous compounds are called lopides f itrcscentes; either from their heiiw some times employed instead of sand in the compo- sition of glass; or because, when mixed with an al- kali, tbcy easily vitrify. Almost all the natural forms of silex contain more than nine tenths of the pure earth; the other constituent parts are in general alu- mine, and oxyd of iron, either separate or com- bined. Quartz. This term is applied to the several varieties of the substance called rock crystal, and sometimes also to other minerals resembling it: M'allcrius, speakincr of