Geology Reference
In-Depth Information
The fact that certain rocks break with a conchoidal fracture came in very handy for prehistoric human
cultures. Stone Age societies depended on rocks with conchoidal fracture characteristics to create
sharp-edged tools and weapons.
When minerals (and rocks) fracture conchoidally, they break off pieces of stone, called
flakes.
With
enough flakes broken along the edge, a rock becomes very sharp, like a knife. Stone toolmakers used
techniques of
flint-knapping,
or specialized rock-breaking, that took advantage of the conchoidal frac-
turing of certain rocks to create useful shapes and sharpened edges.
Some of the earliest stone tools were simple chopping tools, where only one edge was sharpened by
breaking off pieces. But later, as the human brain developed and toolmakers refined their flint-knapping
techniques, beautifully intricate stone tools, such as the spear points of Clovis culture found across
North America, were created. The figure here shows what a Clovis spear point from about 13,000 years
ago looks like.
If it tastes like salt, it must be halite: Noting
unique mineral properties
Some minerals have distinguishing properties of taste or smell. If you have ever seen a
geologist licking a rock, this may be the reason. For example, the mineral halite is salty.
Because halite looks just like calcite, the salty taste is a useful way to distinguish halite
from calcite.
