95 
TAR COMLVITT 
QUARTZUM argillo-pyritaceum. 
Pyritaceous or Alum Clay. 
Ciass 2. Earths. | Order 2. Mixed. 
Gen. 2. Farinaceous Quartz. Spec. Mixed with Argilla and 
Sulphuret of Iron. 
Syn. Pyrito-bituminous Aluminous Ore. Kirw. 2. 17. 
Argillaceous Schistus. Bal. 62.* 
Alum Slate. Jameson, 1. 323. 
Tue Alum Clays vary much at the different places where 
they are found, and may be divided into many tolerably ‘ 
distinct varieties, from the appearance of common black 
Clay to a more slaty one, more or less indurated. They 
do not adhere to the tongue, nor take a ‘polish readily by 
being rubbed with the finger nail, but rather a crumbly 
whitish streak. Aluminous Clay is sometimes glossy with 
a slaty fracture, but otherwise very dull, except having 
some glistening particles of Pyrites. 
Some sorts effloresce readily in the common air—see 
tab. 23 and 24—-and some become covered with a whitish 
tasteless powder. The mixture, like other Clays, may 
contain many adventitious substances, particularly veyetable 
and animal. At Whitby*, Bolton and Stowbrow works, 
in Yorkshire, vegetable impressions, the remains of wood 
and various shells, are found in the Clay. I have very curious 
specimens of the different changes of vegetables, from 
Whitby, in petrifactions from bituminous coaly formations 
to the finest plank jet, if I may so term’it, and some curious 
shelly remains, of which last sort are the Cornua ammonis 
—see tal. 30—which are commonly called Snake-stones ; 
and to favour the idea, the people who gather them form 
one end into a kind of head. 
Among the remains of shells, some there are almost all 
Pyrites ; as the specimen now figured, from Whitby, being 
the remains of a large Pecten or Ostrea, is formed with 
= Cae specimen from Whitby appears from its colour to have been 
roasted. 
