134 Mr. Haidinger on Euchroite, a Nero Mineral. 



its proper place, as it does not seem to have yet been describ- 

 ed even in the foreign journals. 



Form, prismatic, P = 119° 7\ 81° 47', 120° 54'. 

 (a : b : c = 1 : ^0.928 : ^0.344). Approximation. 



Simple forms. P — o> ( P ) ; P + ex ( M ) = 117° 20 < 



(Pr + oo) •'(*) = 95° 12'; (Pr 4- u>) 5 (/) = 78° 47'; Pr 

 (n) = 87° 52'; Pr +00 (k.) 



Combinations, l.P — x.Pr.P+cto. (Pr + ctf . 

 Plate III. Fig. 29. 2 . P — oo . Pr . P + oo . (Pr + a)' . 



(Fr + od) 3 . Pr 4- op, Fig. 30. 



Cleavage, indistinct, parallel to the horizontal prism «, 

 and to the vertical prism m, very much interrupted. Frac- 

 ture, small conchoidal, uneven. Surface, the vertical prisms 

 striated parallel to their common edges of intersection, the 

 horizontal prism smooth, P — cr. often rounded, as if a drop 

 of the solution had remained after the complete formation of 

 the crystal. 



Lustre, vitreous. Colour, bright emerald-green. Streaky 

 pale apple-green. Double refraction, considerable. Semi- 

 transparent, translucent. 



Rather brittle. Hardness = 3.5 . . . 4.0 (very near the 

 same as fluor). Sp. gr. = 3.389. As the specimen employ- 

 ed was not entirely free from the oxide of iron, it is possible 

 that the specific gravity is a little higher, though this can be 

 but very inconsiderable. 



Observations. 



1. The specimen of Euchroite to which the preceding de- 

 scription refers, was purchased last summer by Mr. Allan when 

 in London, from Mr. Sowerby, who had received the mineral 

 from Mr. Bartsch of Vienna. It has been found at Libethen 

 in Hungary, and occurs in crystals of considerable size, in 

 fissures in the common quartzoze mica slate of that locality; 

 Some of the crystals in Mr. Allan's specimen are upwards of 

 three lines in every dimension, though the most perfect crys- 

 tals are much smaller. They are in no small degree like those 

 of Dioptase, and will enter the genus Emerald-malachite of 

 Mohs. 



