IgJ ON THE MEIONITE. 



in tlie Ephemerides of baron Moll*, and which I shall here 

 attempt to answer. 

 First noticed ff^y. Q,^^ ^^^^ knowledjre of this substance we are indebted 



by Rome de 



t*isle to Rome de I'IsIe. This philosopher, guided by the ana- 



asa jacinth logy of the figures of their crystals, has united under the 



with sonie name of jacinth, in the second edition of his immortal work 

 ether subs tan» ,, r ■, i f i- 



tes. f^n crystailogvaphy, several- substances, that now form dir^ 



tinct species. These however he was far from considering 

 as the same, though he did not think proper to distinguish 

 them by different names, which he must have invented for 

 the purpose. In the description he has given of the second 

 variety of the jacinth the dioctaedral variety of the me'io- 

 ulte is easily recognized^ Beside \U locality in the lava qf 

 Somma, and the >vhite colour of the mass, which are pointed 

 out, it is there said, that the two qupdrangular pyramids of 

 the jacinthg the priniitive zircon of Haiiy, are separated 

 by a prism of eight unequal faced, alternately hexagons, an4 

 rectangular parallelograms; and that the latter of these, 

 produced by the truncation of the edges of the prism, some- 

 times very narrow and scarcely perceptible, and at other 

 times more or less broad, always answer to the faces of the 

 pyramids; while the hexagonal sides of the prism are al- 

 ways intermediate to these faces: circumstances that agree 

 perfectly with the dioctaedral meionite. See pi. 6. fig. 5. 

 These separa- ]y[,,^ Haiiy has made four species of the substances de- 

 ited into four •, i i x> ' i i,r i ... 



species by scnbed by Kome de 1 isle. 



Kaiiy, 1. The zircon (the jacinth and jargon of former miner- 



alogists), divisible into an octaedron with isosceles triangular 

 faces, which may be subdivided parallel to planes that would 

 pass through the summits and edges of the faces. 



■2. The harraotome (cross-stone, crvicite, andreolite of the 

 Hartz, staurolite of Kirvvan), divisible into a rectangular oc? 

 taedron, subdivisible on the edges contiguous to the sun^f 

 mit. 



3. The idiocrase (vesuvian of Werner, jacinth of volca- 

 canoes) divisible parallel to the faces and diagonals of ^ 

 right prism with square bases, differing little from a cube. 



* Ueber Haiiy's Mejonit, von Friedrich Mohs: in the Efemeriden der 

 Berg- und Hiittenkunde, herausgegeben von Carl Ehrenbreit Freiherfn 

 ■von Moll, Band II, Lieferurg 1. ^umberg, 1806. 



4. Th€^ 



