252 Professor Necker on Mineralogy considered 



DIVISION I.— ALYSIMOUS CRYSTALS. 



Not sensibly soluble in water ; harder and less brittle than rock>saIt and 

 alum ; tasteless. 



Order I.— ALUMINIDEOUS. 



Chem. Nat. — Alumina and aluminates. 



Insoluble in acids, and infusible before the blowpipe without addition. 

 Completely soluble in the salt of phosphorus (double phosphate of soda and 

 ammonia) into a transparent glass, which does not become opalescent, and 

 without any transparent skeleton. 



Sub. Ord. L— ANHYDRO-ALUMINIDEOUS. 

 With the blowpipe in the matrass not giving out any water. 



Family Gems. 

 Scratch quartz. 



Gen.— Corundum ; chrysoberyll (A ^ S + 2 G A* Seybert) ; spmelle (with 

 pleonaste and gahnite, or zinciferous spinelle). 



Sub. Ord. 2._HYDR0-ALUMINIDE0US. 

 With the blowpipe in the matrass giving out water, and becoming opake. 



Family Diasporides. 

 Scratch only glass, some even with difficulty. Decrepitating with the blow- 

 pipe. 



Gen.— Diaspore ; hydro-aluminate of lead (plombgomme). 

 Appendix. — Gibsite. 



Order 11.— STANNIDEOUS. 



Chem. Nat — Oxides of tin. 



Insoluble in acids ; infusible by themselves before the blowpipe, but redu- 

 cible with a strong reductive flame into white and malleable tin. 



Family Stannolites. 

 Scratch glass. Specific gravity 6. Not giving water with the blowpipe m 

 the matrass. 



Gen Oxide of tin, or tinstone. 



Order III.— SILICIDEOUS. 



Chem. Nat. — Silica and silicates. 



Not completely soluble with the salt of phosphorus before the blowpipe, 

 but forming a glass, which becomes opalescent by cooling, and in almost all 

 cases leaving a transparent skeleton of silica. Or neither soluble nor reduci- 

 We. 



Sub. Ord. I.—ANHYDRO-SILICIDEOUS. 



' Affording no water before the blowpipe in the matrass, or merely hygro- 



