Abstract
IN these two papers the author gives an account of the minute crystals included in sapphire, garnets, and several other minerals, which in some cases are arranged in a number of definite planes, so as to give rise to the appearance seen in the so-called “star sapphires.” The essays are illustrated by a plate, which shows the character of the crystals in a very satisfactory manner. The author is, however, not quite correct in thinking that such included crystals had not been previously described by several authors. Söchting, in his excellent work, * gives an account of some facts similar to those observed by Mr. Lea; and Messrs. Sorby and Butler, in their paper on the microscopical structure of rubies, sapphires, & c.† describe “the small plate-like crystals, often triangular in form, with an angle very acute. They are very thin, and arranged parallel to three principal planes of the sapphire,” and are thus precisely like those now figured by Mr. Lea. There can be no doubt that the study of the minute crystals included in minerals often throws much light on their origin, and they play a far more important part than is often supposed, and serve to explain some of the discrepancies met with in their chemical composition.
Notes on Microscopic Crystals included in some Minerals.
By Isaac Lea. From the Proceedings of the Academy of Natural Sciences of Philadelphia. Read February 16 and May 11, 1869.
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Notes on Microscopic Crystals included in some Minerals . Nature 1, 531 (1870). https://doi.org/10.1038/001531d0
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DOI: https://doi.org/10.1038/001531d0