168 IOWA ACADEMY OF SCIENCE Voi.. XXVII, 1920 
Grenville A. J. Cole. — Rocks and Their Origin, 1912, pages 38-42, 
62-63. 
Flint, a form of silica, is described as being the most common 
substance that replaces calcium carbonate in limestone. For three 
paragraphs flint is strictly associated with the chalk of the Creta- 
ceous of England. Then comes the information that casts of 
crinoids are found in the flints of the Carboniferous limestone. 
“Radiolaria have now been well recognized as flint formers, even 
in dark ‘cherts’ of Silurian age.” In a discussion of sandstone 
it is said, “Bands of flint (chert) occur in certain sandstones, 
. These are due to the cementing of certain layers of 
chalcedonic silica.” Toward the end the author makes no attempt 
to conceal the fact that he regards flint and chert as identical. 
W. 0. Crosby. — Tables for the Determination of the Common 
Minerals, 1911, page 84. 
Flint and chert are described as compact or cryptocrystalline, 
and not glassy. 
/. D. Dana. — Manual of Geology, 1895, pages 83, 480. 
Chert is called an impure flinty rock and flint is used in refer- 
ence to the chalk deposits. 
W. B. Ford. — Dana’s Manual of Mineralogy, 1912. 
Flint is placed under the cryptocrystalline varieties of quartz. 
Archibald Geikie. — Textbook of Geology, 1903, page 141. 
There is no strict definition. Flint is assigned to chalk but it 
is held that chert is impure flint most of which occurs in lime- 
stone. 
A. W. Grabau. — Principles of Stratigraphy, 1913, pages 764-765. 
“Flints characterize chalk, and chert layers abound in many 
limestones. Chert concretions occupy the same relation to lime- 
stone that flints do to chalk.” Thus flints are assigned absolutely 
to chalk and cherts to limestone. 
A. J. Jukes-Brown. — The Building oFthe British Isles, 1911. 
Throughout scattered pages the term “cherts” is used only in 
connection with sands and limestones; “flint” is used with chalk. 
B. H. Kraus. — Descriptive Mineralogy, 1911, pages 74-75. 
Flint, — “Gray, smoky, brown, , nodular variety (of 
quartz) closely related to chalcedony. It is usually found in 
chalk beds and limestone.” Chert, — “A more or less general term 
applied to hornstone, impure flints or jaspers.” They are thus 
described as more or less general terms. 
