HYDROUS SILICATES—MARGAROPHYLLITIS SECTION. old 
The New Jersey clay-beds of the Cretaceous formation are 
mainly kaolinite, and have been thus formed. In other 
cases permeating waters have washed out the oxides of iron 
present, and. have left the white clay in place. A pure 
kaolinite bed occurs at Brandon, Vermont, along with a 
limonite bed, where the rock decomposed was probably a 
feldspathic hydromica slate. Most of the limonite beds of 
Western New England afford kaolinite ; yet it is generally 
more or less colored by iron oxide. 
Common clays consist of finely-powdered feldspar, quartz, 
and other mineral material, with often more or less kaoli- 
nite. They burn red in case they contain iron in the state 
ordinarily present in them of iron carbonate, or hydrous 
iron oxide (limonite), or in combination with an organic 
acid, or in some other alterable state of composition, beat 
driving off the carbonic acid or water, or destroying the or- 
ganic acid, and so leaving the red oxide of iron (or sesqui- 
oxide), or favoring its production. But the iron may be so 
combined as not to give the red color; and this has been 
found to be true with the clays from which the cream-col- 
ored Milwaukee (Wisconsin) brick are made, and that of 
other clay beds in that vicinity. ‘The iron may be there in 
the state of the silicate, zoisite, or epidote. 
Pure kaolinite (or kaolin as it is ordinarily called) is 
used in making the finest porcelain. For this purpose it is 
mixed with pulverized feldspar and quartz, in the proportion 
needed to give, on baking, that slight incipient degree of 
fusion which renders porcelain translucent. The name 
kaolin is a corruption of the Chinese word A’auling, mean- 
ing high ridge, the name of a hill near Jauchau-Fu, where 
the mineral is obtained; and the petuntze (peh-tun-tsz) of the 
Chinese, with which the kaolin is mixed in China for the 
manufacture of porcelain, is, according to 8. W. Williams, 
a quartzose feldspathic rock, consisting largely of quartz. 
The word porcelain was first given to China-ware by the 
Portuguese, from its resemblance to certain sea-shells called 
Porcellana; they supposed it to be made from shells, fish- 
elue, and fish-scales (S. W. Williams). 
The impure kaolin is used for stoneware and fire-bricks. 
The presence of iron, in any state, makes a clay more or 
less fusible, and therefore an unfit material for fire-bricks. 
But, a little of it exists in all clays employed for making or- 
dinary bricks, and hence their red color. 
