478 



MINERALOGY. 



Conchoids! 



Oryctogno- Sal Ammoniac of Vesuvius. 



^_ '*". Coruliluent Parts, Muriate of ammonia, 99.5 

 "~Y~* Muriate of soda 0.5 100.0 



Klaproth, Beit. b. iii. s. 91. 



Geognoslic Situation. As its name implies, it is a 

 volcanic production, occurring in the fissures, or on the 

 surface of volcanic or pseudo-volcanic rocks. 



Geographic Situation. Europe. It occurs in the vi- 

 cinity of burning beds of coal, both in Scotland and 

 England. It is found in the Island of Iceland. On 

 the Continent it is met with at Solfatara, Vesuvius, 

 ./Etna, the Lipari Islands, and Tuscany. 



Asia. Thibet, Persia, and the Isle of Bourbon. 

 America. In volcanic districts both in North and 

 South America. 



SECOND SUBSPECIES. 



CONCHOIDAL SAL AMMONIAC, Jameson. Muschlicher 

 , Karsten. 



Erlernal Characters. Colour greyish-white. Oc- 

 curs in angular pieces. Surface is uneven. Externally 

 glimmering ; internally shining and vitreous. Frac- 

 ture nearly perfect conchoidal. Fragments indetermi- 

 nate angular. Semi-transparent or transparent. Mal- 

 leable. Soft. Light. Taste pungent and urinous. 



Constituent Parts. Muriate of ammonia 97-50 



Sulphate of ammonia 2.50 100. 

 Klaprolh, Beit. b. iii. s. 9*. 



Geognostic and Geographic Situations. This mineral 

 is said to occur, along with sulphur, in rocks of indu- 

 rated clay or clay-slate, in the country of Bucharia. 



Uses. This salt is used for a variety of purposes. 

 Great quantities of artificial sal ammoniac are annually 

 exported from this country to Russia, where it ap- 

 pears to be used by dyers. It is employed by copper- 

 smiths, to prevent the oxidation of the surface of the 

 metals they are covering with tin. It renders many 

 metallic oxides volatile, and is frequently used to sepa- 

 rate metals from each other. 



Sulphate of * MASCAGNINE, or SULPHATE OF AMMONIA. MaS- 

 Ammonia. cagnin, Karsten. 



External Characters. Colours yellowish-grey, le- 

 mon-yellow. Occurs in meally crusts, or stalactitic. 

 Internally dull or glistening. Fracture uneven or ear- 

 thy. Semi-transparent or opaque. Taste sharp and 

 bitter. 



Chemical Characters. It is easily soluble in water ; 

 partly volatilised by heat ; and becomes moist on expo- 

 sure to the air. 



Constituent Parts. It is a compound of ammonia, 

 sulphuric acid, and water. 



Geognoslic and Geographic Situations. It occurs 

 among the lavas of ./Etna and Vesuvius ; in the Solfa- 

 tara by Puzzaeolo ; in the lagunes, near Siena in Tus- 

 cany ; and on the bottom of a hot spring in Dauphiny. 



GENUS VIIL ROCK-SALT. 



Steinsak, Werner and Mohs. 



BOCK SILT. Many axes. Cleavage tessular. Taste saline. Hard- 

 ness =2.02.5 Sp. gravity =2.1, 2.2. 



Hexahe- 1. HEXAHEDflAi. ROCK-SALT, Jameson. Hexaedri- 

 sches Steinsalz, Mohs. 



Tessular. Cleavage hexahedral. 

 This species is divided into two subspecies, viz. rock- 

 salt and lake- salt. 



Oryctogno- 

 sy. 



dral rock 

 salt. 



FIRST SUBSPECIES. 

 ROCK-SALT. Steinsalz, Werner. 



This subspecies is divided into two kinds, viz. Foli- 

 ated rock-salt and fibrous rock-salt. 

 First Kind. 



FOLIATED ROCK-SALT, Jameson. Bl'attriches Stein- 

 salz, Werner. 



External Characters. Its most common colours are Foliated 

 white and grey. Of white, it occurs greyish, yellow- rock salt, 

 isli, and milk-white ; but it seldom approaches to snow- 

 white. Of grey, ash, smoke, and pearl grey. From 

 pearl-grey it passes, though rarely, into flesh, blood, 

 and brick red. Still seldomer do we observe the white 

 varieties marked with Berlin, azure, violet, or lavender 

 blue spots or patches. It is said also to occur ochre- 

 yellow, wine-yellow, and emerald-green. It occurs 

 massive, disseminated, in minute veins, in crusts, plates, 

 and stalactitic ; also in distinct concretions, which are - 

 large, coarse, small, and fineangulo-granular, and these 

 sometimes incline to prismatic t. On the fresh frac- 

 ture shining or resplendent, lustre resinous. Fracture 

 conchoidal. Fragments cubic. In general it is strong- 

 ly translucent, sometimes seuiitransparent and trans- 

 parent. Feels rather greasy. Rather brittle, and 

 easily frangible. 



Second Kind. 



FIBROUS ROCK-SALT, Jameson. Fasriges Steinsalz, Fibrous 

 Werner. rock-salt. 



External Characters. Colours greyish, yellowish, 

 and snow white ; from these it passes into ash and 

 smoke grey ; more rarely it is marked with stripes of 

 flesh red, violet, sky, and Berlin blue. Occurs mas- 

 sive and dentiform ; also in distinct concretions, which 

 are coarse and fine, and straight and curved fibrous. In- 

 ternally it is shining and glistening, and the lustre is 

 resinous. The fragments are splintery. Strongly trans- 

 lucent, verging on semi-transparent. In other charac- 

 ters it resembles the preceding kind. 



Chemical Characters. It decrepitates briskly when 

 exposed to the action of the blowpipe, or when laid on 

 burning coals. Cheshire Kock-Salt. 



Constituent Parts. Muriate of soda 983 

 Sulphate of lime 6^ 

 Muriate of magnesia O^V 

 Muriate of lime 0^ 

 Insoluble matter 10 1000.0 

 Henry, Philosophical Transactions for 1810, pt. i. p. 97. 



Geognostic Situation. It occurs in transition rocks 

 in Switzerland, and in secondary rorks in Germany, 

 England, and South America. 



Geographic Situation. Europe. The principal de- 

 posite of salt in this island is that in Cheshire, where 

 there are several beds that vary in thickness from four 

 feet to upwards of one hundred and thirty feet, and al- 

 ternate with clay and marl, which contain compact, fo- 

 liated, granular, and radiated gypsum. Rock salt also 

 occurs at Droitwich in Worcestershire ; and in Ger- 

 many, France, Hungary, and Spain. 



A/rica. Besides the great beds of this mineral found 

 in Europe, it is also very extensively distributed in 

 other quarters of the globe. In the northern part of 

 Africa, on both sides of the Atlas Mountains, vast quan- 

 tities of rock-salt occur. In the valley of Egarement 

 there are beds of rock-salt resting on gypsum. Mr. 

 Horneman, on his journey from Cairo to Urnmoso^eir, 



j- Some authors describe rock-Hilt in globular and columnar concretions. 



