136 M. Godon’s mineralogical observations. 
yellow of tombac. Some fragments of this species, whien struck by 
the hammer, emit a remarkable metallic sound. _I will no longer in- 
sist on these two rocks, which I have not observed in masses of con- 
siderable magnitude. 
12. I terminate the series of the species of amphiboloid, by that 
which admits talc in its composition (Talcous amphiboloid). This 
rock seems to consist entirely of black amphibole, and talc of a dark 
green colour, which, when the rock is fresh broken, is perceived even 
under the forin of thin hexagonal lamina: All the parts of this rock 
appear sensible to the magnet, though the magnetic sulphurated iron, 
which exists in it, may not always be discernible. 
_ This aggregate has neither the hardness, nor the tenacity, ascribed 
to amphiboloid. When exposed at the surface of the soil, it under- 
goes a rapid decomposition, and occurs with a spheroidal or elliptical 
shape, the surface of which is formed of thin, concentric strata with- 
out adhesion, involving a kernel of the some rock, which had not suf- 
fered alteration. ‘This decomposition is similar to that of some rocks, 
observed in volcanic countries, and considered sumetimes as lavas. 
Talcous amphiboloid is observed forming, in felsparoid, a subordi- 
nate stratum, directed from northwest to sout heast. [ Braintree, on the 
Braintree and Weymouth turnpike 4]. The irface of the stratum 
occurs with an appearance somewhat slaty, and some parts of it pres 
sent an uniform texture, with the same hardness.and colour, which 
indicates that this rock unites to that, which will be described undet 
the name of argilloid. 
Felsparoid. 
_ 13. The above description spreads some light 6n the nature of 
this rock, which is distinguished from the preceding, merely by anars 
tificial consideration; In fact, by observing it attentively we find; 
