Page:Proceedings of the Royal Society of London Vol 1.djvu/106

Rh like felspar or adularia, and partaking of many of the properties of corundum itself, and even of its crystallization. 2. Fibrolites, which are described as small masses frequently crystallized, but different in some respects from all other mineral substances hitherto known. 3. Thallite, or the Epidote of Abbé Hauy. This is minutely described in three different states. 4. Harnblende, which is most constantly and most abundantly contained in the matrix here treated of. 5. Quartz, Talc, Mica, Steatite, Garnets, Zircon; all which, though manifestly dispersed in this matrix, are yet less frequent. And lastly, the presence of black Oxide of Iran is likewise evident, though not in such large proportions as in the matrix of the imperfect corundum from China.

Section 2. Of the matrix of imperfect corundum from China, and the substances with which it is necompanied.~——This matr'ur is totally different from the preceding one, being a granite rock, composed of an aggregate mixture of felspar, ﬁbroljte, mica, and attractable black oxide of iron: but none of that particular substance which has been mentioned as forming the basis of the preceding matr'ur is here ob- served. The four substances above mentioned are unequally distri- buted throughout the mass; some pieces being composed almost entirely of only one of them, while in other pieces the substances are mixed together in diﬂ’brent proportions, and sometimes in nearly equal ones.

Section 3. 0f the matrix of perfect corundum from the Island of Ceylon, and the substances of which it appears to be composed.— The author, on this head, speaks with some diﬂidence, as the precious stones comprised under the denomination of this kind of comndum are selected by the inhabitants from the sands washed down by the rivers or rivulets of the island, and have seldom been brought to Europe in any kind of matrix. He gives us, however, a list of the substances which compose the sands that are sent to us from Ceylon; although he will not venture to assert positively that these substances really accompany the corundum when in its matr'ur. They are, l. Spi- nelle Ruby, which generally composes nine parts in ten of the whole mass of this sand, but in such small crystals or fragments as to render them of little or no consequence in trade; owing, no doubt, to the selection made in India before it is sent over. The few of a tolerable size that have been obtained, are here described as to their crystal- line form, their colours. their peculiar matrix, in some of which was found an iron ore hitherto unknown, while some of them appeared evidently to be masses of adularia. 2. Tourmalin, in the form of a very obtuse rhomboid, with several varieties deducible from this form, and of different colours. 3. Ceylonite, so called by M. In Matherie, but distinguished by the name of Pleonaste in the Minm'alogy of the Abbe Hauy. This is likewise of a variety of crystalline forms and colours. 4. Zircon, which, next to the Spinelle. is the substance most frequently found in the sand of Ceylon, the crystals of which, though very small, are yet in general very perfect. And lastly. though their numbers be very insigniﬁcant, some small scattered