^Chalcedony. Under this, head may he 
grouped a number of varieties of silica 
(see Quartz), including flint, chert, horn- 
stone, jasper, agate, novaculite in part, 
onyx, carnelian, etc., most of which were 
used by the aborigines in the manufac- 
ture of flaked implements. The distinc- 
tions between these rocks have not been 
sharply drawn by mineralogists, and the 
archeologist must be content with group- 
ing them according to their resemblance 
to recognized types. The term flint has 
come into somewhat general use among 
archeologists for the whole . group, but 
this is not sanctioned by mineralogists. 
Chalcedony is a translucent and variously 
tinted indistinctly crystalline variety of 
silica. It is formed by infiltration in 
cavities in the older rocks, as a secondary 
product during decomposition of many 
rocks, and as accumulations of the. sili- 
ceous residue from various organisms. 
It occurs as nodules distributed through 
sedimentary strata, as in the middle 
Mississippi valley; as thin, more or less 
interrupted layers, as in Wyandot cave, 
Indiana, and at Millcreek, 111.; or as 
massive strata, as in Flint ridge, Ohio, 
and on the Peoria res., Inch Ter. Flint 
(true flint), q. v., is formed as nodular 
segregations in chalky limestone, and is 
composed mainly of nearly amorphous 
silica and partially dissolved radiolaria 
and spicules of sponges. The colors are 
dark gray and brownish to nearly black, 
and somewhat translucent on thin edges. 
It occurs extensively in England, France, 
and n. w. Europe, and has recently been 
found in Arkansas and Texas, where it 
was used by the aborigines in making 
implements. Chert, as commonly recog- 
nized, differs from true flint in being 
lighter in color, as a rule, although vari- 
ously tinted and less translucent. It oc- 
curs in the limestones of a wide range of 
geological formations. The best-known 
deposits utilized by the Indians are on 
the Peoria res., near Seneca, Mo., and at 
Millcreek, 111. Ilornstone is the term 
usually applied to varieties of chalcedony 
displaying peculiar horn-like charac- 
teristics of toughness and translucency. 
Much of the nodular chalcedony of the 
Ohio valley, extensively employed by the 
aborigines in the manufacture of imple- 
ments and the blades and disks deposited 
in caches, has been known under this 
name. Jasper (q. v. ) is a ferruginous 
variety of chalcedony, of red, yellow, and 
brownish tints. The greenish varieties 
are known as prase, and these when 
marked with red are called bloodstone. 
Numerous aboriginal quarries of jasper 
occur in e. Pennsylvania. Agate is a 
banded variety of chalcedony found 
mainly in cavities in igneous rocks. The 
natural colors are white to gray, passing 
into various delicate tints. Onyx is a 
banded variety of agate, but owing to 
fancied similarities the name has been 
applied to certain calcareous deposits, as 
the so-called Mexican onyx. 
Consult Dana, System of Mineralogy, 
1892; Merrill, Rocks, Rock-weathering 
and Soils, 1897. See Mines and Quarries, 
Stone-work. (w. h. h. g. p. m. ) 
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