258 



PHYSIOGRAPHY. 



Herrerite Heulandite. 



Color apple green. 

 Very soft ; but brittle. Sp. gr. =3. 



1. It occurs with the above, and would appear to be simply a variety 

 which has suffered partial decomposition. 



HERSCHELITE. 



Primary form. Regular hexagonal prism. 

 Secondary form. Primary, having its terminal edges replaced, 

 the new planes inclining to the bases under 132. 

 Fracture conchoidal. Surface rough. P dull and curved. 

 Color, white. Translucent . . . opake. 

 Hardness = 4-0 ... 5-5 ? Sp. gr, = 2-11. 



1. It is believed to have in general, the composition of Feldspar or 

 Leucite. 



2. It is found with Olivin, at Aci Reale in Sicily. 



3. It appears to be related to Nephiline ; but further researches are 

 required to settle its specific character. 



HETEROSITE. (See Triplite.) 



HEULANDITE. He mi-prism* tic Kouphone- 



Spar. MOHS. 



Primary form. Right oblique-angled prism. M on T 

 = 130 30'. 



Fig. 241. 



Secondary form. 



M on a 



T on a - 



P on a 



M on / - 



J on f 



P on 6 - 



P onb - 



Cleavage, P highly perfect. Fracture imperfectly con- 

 choidal, uneven. Surface of all the faces more or less un- 

 even ; P often concave, M and T convex. 



