MANUAL OF NATURAL HISTORY. 603 



Salts of baryta tinge flame yellow, sulphuric 

 acid throws down a heavy white precipitate 

 with those which are soluble. Symb. Ba. 



3. Family. — Strontiides. Minerals containing com- 



pounds of Strontium. Occur, ] , as Sulphate 

 of Strontia or " Celestine/' in right rhombic 

 prisms, H. 3~3'5, sp. gr. 3*9, bluish-white, 

 very brittle ; 2, as Carbonate or " Strontia- 

 nite/' trimetric, often fibrous or granular, 

 H. 3 •5-4, sp. gr. 3*6, greenish, brittle ; 3, 

 combined with Baryta, as "Barystrontianite/' 

 in Orkney. Salts of strontia colour flame 

 deep red, those which are soluble act with 

 sulphuric acid like those of Baryta. Symb. Sr. 



4. Family. — Calciides. Minerals containing com- 



pounds of Calcium. Occur 1, as Sulphate of 

 Galcia (lime) or "Gypsum/" in right rhombic 

 prisms, sp. gr. 2*3, H. = 1-5 — 2; when tran- 

 sparent it is Selenite, when massive Alabaster, 

 when fibrous Satin-spar, and when an- 

 hydrous, H. = 3 — 3*5, it is Anhydrite; 2, as 

 Carbonate, rhombohedral, sp. gr. 2*6, H. = 

 2*5 — 3*5, when in transparent crystals it 

 is Calcareous-spar or Iceland-spar; when 

 massive, Limestone; when compact and finely 

 crystallized, Marble; when bituminous, Stink- 

 stone; when earthy, Chalk; when projecting 

 from the roof, or on the floor of caverns, &c, 

 Stalactites or Stalagmites; when encrusting 

 Calcareous-tufa, and when in rhombic-prisms, 

 H. = 3 5— 4, it is Arragonite; 3, as Phosphate 



D D 2 



