THE USE OF THE TERMS FLINT AND CHERT 
WALDO S. CLOCK 
Reference to almost any two text books in geology will show 
that there are different usages for the terms flint and chert. Per- 
haps much of the confusion is due to the fact that the origin of 
these substances is unknown, in which case exact definition at 
this time would be premature. Whatever the reason it seems ad- 
visable to bring out the variability of definition, if for no other 
purpose than to state a problem without attempting its solution. 
Blackweider & Barrows. — Elements of Geology, 1911, page 39. 
Flint is defined as “a very compact, dark grey, siliceous rock.’' 
Farther on, chert is said to be “an impure flint, usually of light 
color both occur in limestones. 
Chamberlin & Salisbury.- — Introductory Geology, 1914, pages 268, 
287-289. 
“Flints and cherts occur in limestone both as nodules and as 
distinct beds.” Under alterations of rocks it is stated that silica 
which was primarily deposited as shells is later gathered into 
nodules or concretions of chert or flint. Concretions of chert 
(silica) are common in limestone. Preference is given to mode of 
occurrence, while no distinction is drawn between the two terms. 
Chamberlin & Salisbury. — Geology, Advanced course, 1904, Vol. 
I, page 426. 
There is here no essential difference in the use from that in the 
“Introductory Geology” except that cherts are termed impure 
flints and that both may occur in limestone and chalk. In a ref- 
erence list of the more common minerals under which it is ad- 
mitted that common usage is more or less inconsistent, the defi- 
nitions are given : chert — “an impure flint, usually of light color 
and occurring abundantly in concretionary form as nodules in 
certain limestones ;” flint — “a compact dark chalcedonic or lithoid 
form of quartz.” No sharp rules are laid down. 
H. F. Cleland. — Geology, Physical and Historical, 1916, page 77. 
“Flint and chert are gray to black, translucent to opaque, quartz 
masses which occur in chalk and limestone.” 
