164 PHYSIOGRAPHY. 



Datholite Diallogite. 



3. It occurs in beds of iron-ore, in primitive rocks, accompanied by 

 Calcareous Spar; sometimes also by Fluor, Hornblende, Quartz and 

 Prehnite : with the latter species, and several others of the Zeolite fam- 

 ily, it is found in agate balls and irregular veins in trap-roeks. 



4. Upon the beds of iron-ore at Arendal in Norway, are found the va- 

 rieties of Datholite and Botryolite. The Humboldtite occurs in agate 

 balls in the Seiseralp in the Tyrol, and in irregular veins in greenstone 

 in Stlisbury-craig near Edinburgh. 



In the United States, in New Jersey at Paterson, the Datholite ha 

 been met with in large and well denned forms, in trap ; and at Middle- 

 field in Connecticut, the variety Humboldtite occurs under similar cir- 

 cumstances, and in cavities; also on Mt. Carmel, at Hainden, (Conn.) 

 with Prehnite. 



DERMATIN, (See Kerolite.) 

 DEWEYLITE. (See Kerolite.) 



DIALLOGITE. Macrotypous Parachrose- 

 Baryte. MOHS. 



Primary form, a rhomboid. P on P=106 51'. 



Secondary form, the primary having the upper edges re- 

 placed by tangent planes. 



Cleavage, parallel to the primary form. Fracture une- 

 ven, imperfectly conchoidal. Surface streaked parallel 

 with* the edges of the new planes, thus producing lenticular 

 crystals. 



Lustre vitreous, inclining to pearly. Color various 

 shades of rose-red, partly inclining to brown. Streak 

 white. Translucent in different degrees. 



Brittle. Hardness =3*5. Sp. gr. =3-592 of the crys- 

 tallized variety from Kapnik. 



Compound Varieties. Globular and botryoidal shapes : 

 surface sometimes smooth, at other times rough ; compo- 

 sition columnar, often indistinct. Massive : composition 

 granular, sometimes small, and even impalpable ; some- 

 times it is columnar. 



