110 



SALTS OF BARYTA. 



Obs. The most important foreign localities of witherite 

 are at Alstonmoor in Cumberland, and Anglezark in Lan- 

 cashire. 



Uses. This mineral is poisonous, and is used in the north 

 of England tor killing rats. The salts of baryta are made 

 from this species : these salts are much used in chemical 

 analysis ; the nitrate affords a yellow light in pyrotechny ; 

 the prepared carbonate is a common water color. 



Barytocalcite occurs at Alstonmoor in Cumberland, England, in 

 whitish oblique rhombic crystals, M : M=106° 54'. H=4. G=s3'6— 

 3*7. Consists of the carbonates of lime and baryta. 



Bromlite is a mineral of the same composition from Bromley Hit 

 near Alston, and from Northumberland, England. Its crystals are right 

 rhombic prisms. 



Drcelite is a compound of the sulphates of baryta and lime, occurring 

 in small white crystals in France. 



Zulphato-carbonate of Baryta occurs in six-sided prisms. 



5. STRONTIA. 

 The salts of strontia have a high specific gravity, it 

 ranging from 3*6 to 4*0. In this respect they most resemble 

 the salts of baryta, and they are distinguished by the same 

 characters as the baryta salts from the salts of the metals. 

 Hardness below 4. 



celestine. — Sulphate of Strontia. 



Trimetric. In modified rhombic prisms. M : M = 104° 



to 104° 30'. Crystals sometimes flattened ; often long and 

 slender, a : a = 103° 58'. Cleavage distinct 

 parallel with M. Massive varieties : columnar 

 or fibrous, forming layers half an inch or more 

 thick with a pearly luster ; rarely granular. 



Color generally a tinge of blue, but sometimes clear white. 



Luster vitreous or a little pearly ; transparent to translucent. 



H - 3—3-5. Gr = 3-9—4. Very brittle. 



Composition : sulphuric acid 43*6, strontia 56*4. De- 



crepitates before the blowpipe, and on charcoal fuses rather 



easily to a milk white alkaline globule, tinging the flame 



red. Phosphoresces when heated. 



How is witherite distinguished from strontianite ? What are itsuses 1 

 What is said of the salts of strontia 1 What is the usual color and 

 appearance of celestine 1 What is the composition 1 



