18 PHYSIOGRAPHY. 



Magnesite. 



LYDJAN STONE. (See Quartz.) 



MACLE. (See Andalusite.) 



M ACLURITE. (See Brucite.) 

 MAGNESITE. Staphyline Lime-Haloide. 



Reniform, tuberose, massive. Composition columnar, 

 individuals very delicate and diverging, producing a silky 

 lustre; also impalpable. Fracture flat conchoidal, some- 

 times fine earthy. 



Dull. Color yellowish grey, cream-yellow, yellowish 

 and greyish white. Streak white and greyish white. Fee- 

 bly translucent on the edges . . . opake. 



Sp. gr. = 2*808. (No allowance being made for its 

 imbibition of water.) 



Adheres pretty strongly to the tongue. 



1. Several varieties of the present species are distinguished by parti- 

 cular denominations. 1. Meerschaum or Sea-foam, which is contamina- 

 ted with variable proportions 6f silica : it is opake, and possessed of an 

 earthy fracture, yields easily to the nail, and adheres strongly to the 

 tongue ; occasional!}' it is very porous, so as to swim on water. Sp. gr. 

 = 1*2 . . . 1-6. According to BERTHIER, a specimen from near Madrid, 

 consisted of magnesia 23-8, silica 53 8, water 20 0, alumina 1-2. 2. Com- 

 pact Carbonate of Magnesia. Color snow-white. Sp. gr. = 2-56. 

 Gives sparks with steel, but does not scratch Fluor. It dissolves in acids, 

 at ordinary temperatures, with extreme. slowness, even when finely 

 powdered; but by heat, its solution is quickened, attended with the ex- 

 trication of carbonic acid gas. According to Dr. HENRY, it consists of 

 magnesia 46, carbonic acid 51. 3. Pulverulent Carbonate of Magne- 

 sia. It is in the form of a light, white, powder, or in slightly cohering 

 masses, resembling chalk. It appears to have resulted from the decom- 

 position of Native Magnesia. It consists, according to WACHTMEISTER, 

 who analysed a specimen from Hoboken, of magnesia 42*41, carbonic 

 acid 36-82, water 18 53, silica and oxide of iron 2-23. 



2. Before the blow-pipe, it is infusible. It dissolves with a slow effer- 

 vescence in the nitric and dilute sulphuric, acids. 



