128 5 [BtfokVL 



CHAP. XXH* 



M A N G A N E S E. 



Datura! Hiftory cf Manganefe. Its Ejj'tJls on Glafs.Regulus or Me* 

 tal. Black Wad, IVlanganefe contained in Vt^etablcs. U/es in 

 the Arts* 



9" R S HIS metal is almoft always found in the flate 

 JL of calces, which vary much in colour and ap- 

 pearance; they are white, blue, yellow, red, dark 

 green, arid black, according as they are united with 

 more or lefs oxygen, or contaminated v ith foreign 

 fubflances. The darker coloured the ores, the more 

 oxygen they may be fuppofed to contain, as any 

 procefs which deprives them of this principle always 

 renders them paler. Manganefe is alfo found cryf- 

 tallized in a vaTiety of forms. Many naturalifts, 

 judging by their colour, and the ochry * cruft with 

 which they are often furrounded, have ranked the 

 calces of manganefe among the iron ores. The black 

 calx of manganefe gives a violet, purplifh, and fome- 

 times a reddifh tinge to tranfparenc glafs ; but when 

 added in a fmall quantity to that which has a blueifh 

 Or greenifh caftj it produces only a flight dulkineisi 

 tvithout a predominancy of any colour. 



The regulus of manganefe is ver/ difficultly ob- 

 tained. Its colour is a dufky white, but its mafies 

 are irregular and uneven from imperfect: fufion. Its 

 fracture is bright and fliining, but it foon tarnifhes and 

 becomes blackim on expoiure to air. When pul- 

 verifed it is always magnetic, though it has^not this 

 property in the mafs. If expofed to air, particularly 



* Ochre being an iron Ore* 



in 



