MINERALOGY. 283 



lustre and is transparent. The hardness is 4, and the specific 

 oravity 4.98. Found at Langban, Sweden, with tephroite, 

 which it closely resembles, with jacobsite, and native lead; 

 described by A. E. Nordenskiold. 



Hibbertite. A hydrated carbonate of calcium and mag- 

 nesium. It is found as a loose lemon-yellow powder imbed- 

 ded in purple kammererite. Found at a chromite mine in 

 the island of Unst; described by Heddle. 



Hullite. A hydrous silicate related to delessite. It is 

 velvet-black, brittle, waxy to dull in lustre. It occurs filling 

 cavities in the basalt of Carnmoney Hill, near Belfast, Ire- 

 land. 



HyaloteTxite. A silicate of lead, barium, and calcium. It 

 is found in coarsely crystalline masses, showing two cleav- 

 ages at right angles, or nearly so, to each other. The color 

 is white to pearl-gray, the lustre vitreous to greasy; it is 

 semi-transparent and brittle. Before the blowpipe it melts 

 to a clear glass, and to this it owes its name. Found with 

 mimetite and schefterite at Langban, Sweden ; described by 

 A. E. Xordenskiold. 



Hydrocerussite. A hydrated carbonate of lead. It ap- 

 pears as a crystalline coating on native lead. This coating 

 consists of transparent quadrangular crystals showing a 

 perfect cleavage. From Langban, Sweden ; described by 

 A. E. Nordenskiold. 



Iodbromite. A mineral containing the bromide, iodide, and 

 chloride of silver. It crystallizes in regular octahedrons, of 

 a sulphur-yellow color ; like the well-knowm cerargyrite, or 

 horn silver (silver chloride), to which it is closely related, it 

 is eminently sectile, so that it may be cut with the knife. 

 Found in cavities in quartz at Dernbach, Nassau ; described 

 by A. von Lasaulx. 



Ionite. A hydrocarbon related to pyropissite. It has a 

 brownish-yellow color and irregular fracture. It occurs in 

 thin seams in the Pliocene argillaceous lignite of lone Val- 

 ley, Amador County, California ; described by S. Purnell. 



Leidyite. A hydrous silicate of aluminium, iron, calcium, 

 and magnesium, supposed to be related to the zeolites. The 

 mineral occurs in wartlike incrustations on grossularite and 

 zoisite ; also occasionally on quartz, and sometimes as small 

 stalactitic forms consisting of pearly scales. It has a grass- 



