BARYTES. 335 



2-13. Before the blow-pipe it becomes soft and friable, and loses 

 weight. It is soluble in sulphuric, nitric, and muriatic acids. Ac- 

 cording to Dr. Bruce, it consists of pure magnesia 70, water 30, 

 in 100 parts. Native magnesia has hitherto been found only in 

 small veins that traverse a rock of serpentine, at Hoboken, in 

 New Jersey. 



Genus III.— BARYTES. 



Baryte, Fr.; Barite, It.; Baryterde; Schwerde, Ger. 



The earth called Barytes exists in nature in combination either 

 with sulphuric or carbonic acid, forming two distinct species of 

 minerals, the Sulphate and Carbonate of Barytes. It is the 

 heaviest of all earthy minerals, except Zircon. Both species are 

 used in pharmacy for preparing the muriate. 



Sp. 1. Sulphate of Barytes, or Heavy-Spar. — (Pl. XLV. 

 fig. 2.) — Baryte sulphate crystalizee, Hai/y; Schwerspath, Werner. 

 — It occurs generally crystalized, also lamellar, fibrous, granular, 

 compact, or earthy. The prevailing colours are greyish, yellowish - 

 white, blueish -white, and red. The crystals are frequently colour- 

 less and transparent, and have a shining vitreous lustre, inclining 

 to pearly. The secondary crystals are generally flat prisms, or 

 tables, and they often occur of considerable size. The specific 

 gravity varies from 4-30, to 4-37. It is brittle, and easily frangible. 

 Its constituents are barytes 67, sulphuric acid 33. Very fine 

 crystals of this variety are found in the lead-mines of Cumberland, 

 Durham, and Westmoreland. Compact Sulphate of Barytes occurs 

 in amorphous masses, which have a lamellar structure; also dis- 

 seminated, reniform, semi-globular, with cubic impressions, and 

 also in curved lamellar concretions. It is found in the mines of 

 Staffordshire and Derbyshire, where it is named Caivk. 



Sp. 2. Carbonate of Barytes, or Witherite. — Baryte car- 

 bonatee, Hauy. Witherit, Werner.— This mineral is rarely crys- 

 talized ; but most frequently occurs in irregular masses, or in distinct 



