MAGNESIA. 



251 



Fig. 124. 



M 



M 



M 



EPSOM SALT. 



[From its having first been found at Epsom, in England.] 



Magnesie Sulfatee. Haiiy. — Sulphate of Magnesia. Ckaveland, PMUips and TTiemson. — Prismatic Epeom 

 Salt. Jameson. — Prismatisches Bitter-Salz. Mohs. — Kpsomite. Beudant. 



Description. Colour white and grey. It occurs regularly crystallized ; also in crusts, 



botryoidal and reniform. The primary form 

 '^' *■ is a right rhombic prism nearly rectangular. 



Fig. 124. M on M' 90° 30'. Fig. 125 is one 

 of the secondary forms, the pyramidee of 

 Haiiy. M on Z 129° 14' ; Z on Z 126° 52'. 

 Cleavage perfect parallel to the shorter di- 

 agonal of the primary. Fracture conchoi- 

 dal. Lustre vitreous. Transparent or trans- 

 lucent. Very brittle. Hardness from 2.0 

 to 2.5. Specific gravity from 1 .66 to 1 .75. 

 Before the blowpipe on charcoal, it is con- 

 verted into sulphuret of magnesium. It dissolves in an equal weight of cold water. Taste 

 bitter. The solution gives with potash a white pulverulent precipitate, which becomes lilac 

 when it is heated upon charcoal, after the addition of a drop of nitrate of cobalt. 



Composition. Magnesia 16.0, sulphuric acid 32 . 53, water 51.43. MgO.SOj-l-TAq. 



Geological Situation. It occurs in alum mines, and in several mineral waters. In this 

 State, it is almost always found as an efflorescence on limestone rocks. 



localities. 



Albany County. Epsom salt, in the form of efflorescences, has been observed in a side- 

 hill near Coeymans landing. On the east face of the Helderberg, in the town of Bethlehem, 

 near Mr. Fryer's, it is found in needleform crystals and in crusts on the surface of an impure 

 water limestone. It is also found in the town of Guilderland. 



Cayuga County. Epsom salt occurs in the eastern ledge of rocks near the head of Cayuga 

 lake, for three or four miles, in connexion with sulphate of iron and thin layers of coal. It is 

 also found at the base of a hill on the east bank of Owasco creek, near Auburn. The same 

 mineral occurs on the slate near Ludlowville. Specimens of the latter, received from Mr. 

 Vanuxem, were found on analysis to be nearly pure. 



It may be here remarked, that Mr. Vanuxem ascribes the columnar form of some of the 

 limestones at the west to the crystallization of the sulphate of magnesia in fibrous crystals at 

 the joints of the rock. The carbon which invests the striae was a subsequent action, probably 

 a deposition from, the same water which dissolved the mineral.* 



* Vanuxem. New-Ymk Geological Reporu, 1838. 



