528 



MINERALOGY. 



Oryctogno- Second Kind. 



\~~-^*j EARTHY BOTRYOLITE, Jameson. Enliger Botryo- 

 Earthy Bo- Hth, Hausmann. 



tryolite. External Characters. Colour snow-white. Small 



botryoidal. Dull. Fracture earthy. 



Geognostic and Geographic Situation. It occurs 

 along with the fibrous kind. 



ZWJLITE. GENUS vi.ZEOLITE. 



Schaum Spath, Mohs. 



Every kind of axis. Hardness ranges from 3.5, to 

 6.0. Sp. gravity from 2.0 to 2.5. 



This genus contains the following species, viz. 1. 

 Dodecahedral Zeolite, 2. Hexahedral Zeolite, 3. Rhom- 

 boidal Zeolite, 4. Pyramidal Zeolite, 5. Di-prismatic 

 Zeolite. 6. Prismatic Zeolite, 7- Prismatoidal Zeolite, 8. 

 Axifrangible Zeolitet. * Wavellite. 



1. DODECAHEDRAL ZEOLITE, or LEUCITE*, Jame- 

 son. Dodecaedricher Schaum Spath, Mohs. Leucit, 

 Werner. 



Tessular. Cleavage hexahedral and dodecahedral. 

 Hardness=5.5 6.0. Specific gravity=2.4, 2.5. 



External Characters Colours white and grey. Sel- 

 dom occurs massive, and in granular concretions, most 

 frequently in roundish imbedded grains, and crystalliz- 

 ed in acute double eight-sided pyramids, in which the 

 lateral planes of the one are set on the lateral planes of 

 the other, and the summits deeply and flatly acuminat- 

 ed by four planes, which are set on the alternate lateral 

 edges. Surface of the grains rough, and dull, or feebly 

 glimmering ; that of the crystals is smooth, seldom 

 slightly streaked, in the direction of trie diagonal, and 

 glistening. Internally the lustre is shining, approach- 

 ing to glistening, and is vitreous, inclining to resinous. 

 Fracture imperfect and flat conchoidal.. Translucent, 

 semi-transparent, and some varieties approach to trans- 

 parent. Refracts single. Brittle. Easily frangible. 



Chemical Characters Before the blowpipe it is infus- 

 ible without addition ; with borax it forms a brownish 

 transparent glass. 



Mean of different analyses. 



Constituent Parts. Silica . 54 



Alumina . 24 

 Potash . 21 



Loss . 1 100 



Klaproth. 



Geognostic and Geographic Sitiations. It occurs 

 principally in secondary trap rocks, and in lavas, and 

 appears to be almost exclusively a production of Italy 



Herahe- 3. HEXAHEDHAL ZEOLITE, or ANALCIME, Jameson. 

 dral Zeo- Hexadrischer Schaum Spath, Mohs. Analcime, Haiti/. 

 Kubizit, Werner. 



Tessular. Cleavage hexahedral. Hardness=5.5. Sp. 

 gravity=2.0 2.5. 



External Characters. Colour white, which passes into 

 flesh-red. Seldom occurs massive, and this variety is 

 disposed in coarse and small angulo-granular concre- 

 tions, which are in general very closely aggregated ; 

 generally crystallized, in the following figures. 1. Per- 

 fect cube. 2. The cube flatly and deeply acuminated 

 on all the angles, with three planes, which are set on 

 the lateral planes. 3, Acute double eight-sided pyra- 



mid, deeply and somewhat flatly acuminated on both Orj ciogi 

 extremities, with four planes which are set on the alter- *X- 

 nate lateral edges. Surface of the crystal smooth, and V "V* 

 splendent or shining. Internally intermediate between 

 sinning and glistening, and the lustre vitreous, inclining 

 to pearly. Fracture small or fine-grained uneven, or 

 conchoidal. Fragments generally indeterminate angu- 

 lar, seldom more or less cubical, owing to the imper- 

 fection of the cleavage. Translucent or semi-trans- 

 parent, and the crystals are transparent. Easily fran- 

 gible. 



Chemical Characters. It melts with intumescence, 

 before the blowpipe, into a transparent glass. 



Physical Characters. By friction, but not by heating, 

 it becomes electric. 



Analcime of Montecchio-Maggiore. 

 Constit. Paris. Silica . 58.0 



Alumina . 18.0 



Lime . 2.0 



Natron . 10.0 



Water . 8.596.5 



Vauqvelin, Annal. du Mus. 

 d'Hist. Nat. t. ix. p. 241. 



Geognoslic Situation. It occurs in primitive and se- 

 condary rocks, but more abundantly in secondary than 

 in primitive rocks. 



Geographic Situation. Itoccursinthe secondary green- 

 stone of Salisbury Craigs, in the porphyritic rock of the 

 Gallon Hill, near Edinburgh, and in many other places 



in Scotland. 



Hnomboi 



3. RHOMBOIDAL ZEOLITE, or CHABASITE , Jameson. dalZeolit 

 Rhomboedrischer Schaum Spath, Mohs. Chabasie, 

 Haiiy. Schabasit, Werner. 



Rhomboid=93 48'. Cleavage rhomboidal. Hard- 

 ness=4.0 4.5. Sp. gravity=2.0 2.1. 



External Characters. Colour greyish-white, approach- 

 ing to yellowish white. Seldom occurs massive ; almost 

 always crystallized. The following are the most, fre- 

 quent secondary forms : 1. Rhomboid truncated on the 

 six obtuse lateral edges. 2. Rhomboid truncated on 

 the six obtuse lateral edges, and on the six obtuse 

 angles. 3. Rhomboid in which each of the original 

 planes of the rhomboid is divided into two. The 

 lateral planes of the crystals are streaked in a pecu- 

 liar manner ; the streaks shoot from the shorter dia- 

 gonal, (the dividing edge of the plane,) and run parallel 

 with the two adjoining lateral edges of the rhomb. 

 The truncating planes are smooth. Externally the crys- 

 tals are splendent ; internally glistening, and the lustre 

 vitreous. Fracture imperfect conchoidal, and also 

 small-grained uneven. Fragments indeterminate an- 

 gular. Translucent ; the crystals sometimes pass into 

 semi-transparent. 



Chemical Character. Before the blowpipe it melts 

 easily into a spongy white enamel. 



Chabasite of the Faroe Islands. 

 Constituent Parts. Silica . 43.33 



Alumina . 22.66 

 Lime . 3.34 



Natron, with Potash 9.34 

 Water . 21.0099.67 



Vauquelin. Annal. de Mus. d'Hist. Nat. t. ix. p. 333. 

 Geognoslic Situation. It occurs principally in second- 

 ary trap rocks; most frequently incavities of amygdaloid, 



Mohs names the eighth species Axenthdkndcr, because its principal cleavage is perpendicular to the axis of the crystal ; and thi Una 

 U here translated axifrangiblc, until a more appropriate one shall occur. 

 ^ Leucite, from Xmnw, w/iifc, and refers to its frequent white colour. 

 * The name C/tabuie, ii from Chabazion, a stone described by Orpheus in his poems, but unknown to us at present. 



