Cave onyx
Encyclopedia
Cave Onyx is an old name for flowstone
.
Onyx was a common term in a certain area of the United States, namely the TAG area and the Ozarks during the 19th and early 20th century. It was used for certain kinds of calcite
speleothem
s which are banded, similar to true onyx
.
The calcite concentrations in cave
s are banded as they are deposited very slowly, layer by layer. The color depends on the climate outside, which changes continually, and the amount of pigments like iron oxide
brought in by the water. So they have typically brown, beige, white and transparent banding. Much rarer are other colors like blue and green, which are typically based on copper oxides.
The true onyx is also banded, and looks very similar. The main difference is; onyx is composed of quartz
, cave onyx is composed of calcite
.
It is easy to determine the difference: with a knife it is possible to scratch calcite but not quartz, several acids show a reaction with calcite but not with quartz. Typically the test with weak hydrochloric acid
is used.
There are numerous caves called Onyx Cave
.
Flowstone
Flowstones are composed of sheetlike deposits of calcite formed where water flows down the walls or along the floors of a cave. They are typically found in "solution", or limestone caves, where they are the most common speleothem. However, they may form in any type of cave where water enters that...
.
Onyx was a common term in a certain area of the United States, namely the TAG area and the Ozarks during the 19th and early 20th century. It was used for certain kinds of calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
speleothem
Speleothem
A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone solutional caves.-Origin and composition:...
s which are banded, similar to true onyx
Onyx
Onyx is a banded variety of chalcedony. The colors of its bands range from white to almost every color . Commonly, specimens of onyx contain bands of black and/or white.-Etymology:...
.
The calcite concentrations in cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
s are banded as they are deposited very slowly, layer by layer. The color depends on the climate outside, which changes continually, and the amount of pigments like iron oxide
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...
brought in by the water. So they have typically brown, beige, white and transparent banding. Much rarer are other colors like blue and green, which are typically based on copper oxides.
The true onyx is also banded, and looks very similar. The main difference is; onyx is composed of quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, cave onyx is composed of calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
.
It is easy to determine the difference: with a knife it is possible to scratch calcite but not quartz, several acids show a reaction with calcite but not with quartz. Typically the test with weak hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
is used.
There are numerous caves called Onyx Cave
Onyx Cave
Onyx Cave may refer to:In the United States:*Onyx Cave , a National Natural Landmark*Onyx Cave , a small show cave*Great Onyx Cave, Kentucky**Great Onyx Cave Entrance, Mammoth Cave, Kentucky, listed on the NRHP in Kentucky...
.