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CURSORY REMARKS 
a 
’ ON THE 
MINERAL SUBSTANCE 
Called, in Derbyshire, 
ROTTEN-STON EL.* 
" 
WILLIAM MARTIN, F.L.S. &c. 
COMMUNICATED BY J. HULL, M. D, F.L. S. 
(Read December 28, 1810.) 
— > Ose 
Me. KIRWAN in his “ Elements of 
Mineralogy,” (vol. i. p. 203.) states, that 
Tripoli is often of pseudo-volcanic and some- 
times, perhaps, of genuine volcanic origin ;— 
he adds, however, that “ it also frequently 
arises from the decomposition or disintegra- | 
tion of other stones.” The latter observation 
appears to apply strictly to our Derbyshire 
Rotten-stone, which is usually considered by 
mineralugists as a variety of Tripoli, origi- 
nating from some unknown decomposed stone 
of the argillaceous kind. 'That the substance 
producing otten-stone is, however, in its 
. 4 
* Cariosus Anglorum, Gmel. Linn. Syst. Nat. p. 146.— 
Tripoli. Kirwan. El. Miner. p. 202, 
Rr 
