Can You Dig? Flowering Tube Onyx

Earlier this week, someone asked me "What is Tube Onyx?" - and honestly I had no idea. So, I did a little research & here's what I found:

Tube Onyx
Country of Origin – U.S.A. (Utah)

Onyx was a common term in the TAG area and the Ozarks during the 19th and early 20th century. It was used for certain kinds of calcite or flowstone which are banded, similar to true onyx. The true onyx is also banded, and looks very similar, so the main difference is; onyx is composed of quartz, cave onyx is composed of calcite, so needless to say cave onyx is a softer stone.

The calcite concentrations in caves are banded as they are deposited very slowly, layer by layer. These are referred to as speleothems. 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.

Flowstones are composed of sheet like 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. However, they may form in any type of cave where mineral rich water enters.

Flowering Tube Onyx Unpolished - photo from Yuku

Flowing films of water that move along floors or down positive-sloping cave walls build up layers of calcium carbonate (calcite), aragonite, gypsum, or other cave minerals. These minerals are dissolved in the water and are deposited when the water loses its dissolved carbon dioxide through the mechanism of agitation, meaning it can no longer hold the minerals in solution. The flowstone forms when thin layers of these deposits build on each other, sometimes becoming rounder as the deposit gets thicker. There are two common forms of Flowstones, Tufa and Travertine. Tufa is usually formed via the precipitation of calcium carbonate and is spongy or porous in nature. Travertine is a calcium carbonate deposit often formed in creeks or rivers its nature is laminated and oftentimes includes such structures as stalagmites and stalactites.

The deposits may grade into thin sheets called "draperies" or "curtains" where they go over overhanging portions of the wall. Some draperies are translucent, and some have brown and beige layers that look much like “cave bacon”.

Polished Tube Onyx Cab - photo from Flicker

As in interesting note: Though flowstones are among the largest of speleothems, they can still be damaged by a single touch. The oil from human fingers causes the water to avoid the area, which then dries out. Flowstones are also good identifiers of periods of past droughts, since they need some form of water to precipitate, the lack of that water for long periods of time can leave traces in the rock record via flowstones. (most of this information came from Wikkipedia.com)