Cave formations are commonly known as “cave onyx.” It is a form
of calcium carbonate which is the same material of which limestone
is made. Its only value is the beauty it adds to the cave.
brittle and will break like glass. The acid from the touch of one’s
hand to cave onyx will destroy the gloss on it and make it dull and
Cave onyx is
formed by surface water which combines with carbon dioxide which is
given off by plants, and forms a mild carbonic acid. The acid
dissolves limestone rock (calcium carbonate) and forms calcium
bicarbonate which is soluable in water. This solution seeps down
into the cave.
limestone will stay in bicarbonate form only as long as the carbon
dioxide is present. Since carbon dioxide is normally a gas, it takes
pressure and low temperature to keep it in the solution.
pressure is furnished by the ground as the solution seeps through
and the coolness is furnished by the natural coolness of the earth.
bicarbonate solution reaches the cave ceiling, the pressure is
relieved and the solution warms up. This releases the carbon dioxide
and the calcium bicarbonate turns back to plain old calcium
carbonate which is not soluable in water so it is deposited on the
cave ceiling or floor in the form of cave onyx.
The rate of
drip is an important factor in the rate of growth and shape of the
formation. If the drip is slow, most of the deposit is left on the
ceiling. If it is fast, the major deposit is left on the floor. A
slow drip makes faster growth than fast drip.
growth of formations is about one cubic inch per 100 years!