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Logging Tasks

At this establishment with a somewhat weird name, it's outer walls are cladded with a unique stone. I couldn't help but create an EC here because of it.

Quick short answers will be good enough here, as I think you should be admiring the stone more than trying to answer these questions.

1. Based on the information given below, would you call green onyx travertine an onyx or a banded calcite/travertine? Why so?
2. Is this travertine formed in warm or cool waters? Why so?
3. In the text about this particular travertine, what other features supports the theory you mentioned in Q2?

Onyx vs Travertine

Onyx is a type of chalcedony, which means it is a silica based rock. What defines onyx is it's banding as shown in the image below.

Here is a very, very simplified formation of onyx:

1. Silica rich solution accumulates in rock cavities.
2. Evaporation leaves behind the silica
3. The silica crystallises forming chalcedony.
4. The banding occurs due to changes in concentration of impurities during the deposition process.

Travertine is a limestone, a calcium carbonate (note the calc part). 

1. Calcium carbonate rich water flows over an area and evaporates, leaving behind the mineral.
2. The minerals form calcite and aragonite, depending on the impurities present will affect the colour.
3. Layers of calcite form - Warmer waters cool slowly allowing larger bands/layers to form. A cooler environment allows living things to thrive around the water, leading to a porous surface and fossil imprints.
4. The layers compact and form travertine!

Note the difference in the banding widths as well as the porous surfaces

Not related to the EC, but someone found a human jaw in travertine.

TL;DR - Onyx is silica, travertine is calcium carbonate. Banded calcite is sometimes marketed as onyx. The chemical composition differentiate them.

Green Onyx... travertine?

The walls of this establishment are what's marketed as Green Onyx Travertine, quarried from Pakistan. This is a little bit of a misnomer.

Volcanic activity during the late Miocene and Pleistocene formed mountains in Balochistan, Pakistan. This is the source of geothermal heat for the hot springs which deposited the travertine. Geochemical analysis of the volcanic rocks, particularly dacite, of the Koh-i-Sultan province shows that both the Balochistan travertine and the Koh-i-Sultan dacite contain the same stronitum (Sr) isotope compositions.

During my research on this topic, I couldn't really find why the green hues exist, although a quote from Abdul Bashir, Chief Geologist at Koh-i-Daleel Minerals mentions "travertine found in igneous rocks is generally harder, often containing jade silicates and calcite". I suppose jade minerals could be responsible.