ORIGIN AND FORMATION OF SOILS. $93 
Chlorite is a common mineral occurring in small scales 
or plates which are brittle. It is soft, usually exists in 
masses, rarely crystallized, and is very variable in color 
and compcsition, though in general it has a grayish or 
brownish-green color, and contains magnesia, alumina, and 
iron, united with silica. See analysis below. 
Leucite is an anhydrous silicate of alumina found 
chiefly in voleanic rocks. It exists in white, hard, 24-sid- 
ed crystals. It is interesting as being formed ata high 
heat in melted lava, and as being the first mineral in which 
potash was discovered (by Klaproth, in 1797). See anal- 
ysis below. 
Kaolinite is a hydrous silicate of alumina, which is 
produced by the slow decomposition of feldspar under the 
action of air and water at the usual temperature. Form- 
ed in this way, in a more or less impure state, it consti- 
tutes the mass of white porcelain clay or kaolin, which is 
largely used in making the finer kinds of pottery. It ap- 
pears in white or yellowish crystalline scales of a pearly 
luster, or as an amorphous translucent powder of extreme 
fineness. Ordinary clay isa still more impure kaolinite. 
CHLORITE. LEUCITE. KAOLINITE. 
Steele Mine, N.C. Vesuvius, Summit Hill, Chaudiere 
Eruption of 1857. Pa. Falls. Canada. 
Genth. Rammelsberg. 8S. W. Johnson. T.S. Hunt. 
Silica, 24.90 57.24 45 .93 46.05 
Alumina, 1.7 22.96 39.81 38.37 
Sesquioxide of iron, 4.60 — — — 
Protoxide of iron, 7A.21 —— — — 
Protoxide of manganese, 1.15 — —— — 
Magnesia, 12.78 —— —— 0.63 
~ Lime, — 0.91 a 0.61 
Soda, — 0.93 —— —— 
Potash, — 18.61 —— 
Water, 10.59 — 14.02 14.00 
Tale is often found in pale-green, flexible, inelastic scales 
or leaves, but much more commonly in compact gray 
masses, and is then known as soapstone. It is very soft, 
