86 



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 Abb6 Hauy. This is minutely described 

 in three different states. 4. Hornblende, 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 Iron 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 accompanied. This matrix is totally 

 different from the preceding one, being a granite rock, composed of 

 an aggregate mixture of felspar, fibrolite, mica, and attractable black 

 oxide of iron : but none of that particular substance which has been 

 mentioned as forming the basis of the preceding matrix 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 different proportions, and sometimes in nearly equal 

 ones. 



Section 3. Of 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 diffidence, as the precious 

 stones comprised under the denomination of this kind of corundum 

 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 matrix. They are, 1 . 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. la Matherie, 

 but distinguished by the name of Pleonaste in the Mineralogy 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 



