# Tag Info

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### How do geologists find ore deposits?

That is the multimillion dollar question! "looking for surface formations" is indeed one way, and it was the main method of exploration in the past. This does not necessarily mean that you directly ...
• 22.8k
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### Can ultrasounds be used to map the density of large underground regions?

Sound-like waves are routinely used to image the subsurface, but mostly well below the ultra-sound band. Several methods involve sound-like vibrations: Reflection seismic — the most important ...
• 10.9k
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### Why would India have so much thorium on its beaches?

why would India have so much thorium on it's beaches...? Because monazite. Monazite is a rare earth element phosphate, with the formula CePO4 (where Ce stands not only for cerium, but all of the are ...
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### How do geologists find ore deposits?

In addition to the above, what happens is that people look for commonalities between known deposits. So, for example, if you have a lot of gold veins in one area, and lots in another area, then you ...
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### How do geologists find ore deposits?

I've been looking for these things over a few decades and along with other geologists doing this we have seen how we find things change somewhat. Many methods used a century ago are still in use, but ...
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### Are there minerals which are not been found on earth but which are still possible to exist?

To answer the first part, there are many minerals on earth which do not involve silicate bonded structures. For instance, non-silicates (minerals of carbonates, sulfides, sulfates, phosphates, and ...
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### Connection between microbes and serpentinite?

The most common explanation for microbial activity in serpentinites is the exploitation of abiogentic hydrogen and methane formed during the serpentinisation process. Quoting the abstract of a recent ...
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### What is the geologic origin of Cryolite, and could there be more?

Ivigtut Cryolite deposit, Ivittuut (Ivigtut), Arsuk Fjord, Sermersooq, Greenland deposit is the first and largest occurrence of Cryolite but it is not the only location to report Cryolite. Some of ...

### Are there any areas on Earth with purplish-colored soil/sand/rock/land?

Soil color is highly dependant on the oxides and other minerals in the composition. Purplish tones appear to be possible by inclusion of manganese oxide compounds. There are locations in China that ...

### Are there probably decent oil fields located in the middle of the ocean?

Are there probably decent oil fields located in the middle of the ocean? tl;dr: no. Hydrocarbon deposits form by thermal maturation (i.e. slow and mild heating) of buried organic matter (i.e. dead ...
• 22.8k
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### What are the cubic formations found inside Larimar gemstones?

Calcite and hematite may not be the the answer to my question Hematite is not the answer, but calcite is. The inclusions are not cubic, they are rhombohedral. This is precisely how calcite looks ...
• 22.8k
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### Where can fluorite be found on Long Island, New York?

I do not know of fluorite being reported to occur on Long Island. If fluorite is found in NYC, the Natural History museum might have specimens. You might try contacting a mineralogy / mineral ...

### Which Earth minerals would Moon colonists miss the most?

The composition of Moon rocks is pretty much the same as that of Earth. However, none of the processes that concentrate specific minerals in one location (i.e. into a mineral deposit useful for mining)...
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### What kind of purple stone is this?

That's amethyst, a violet version of quartz See here
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### How do hematite and magnetite form?

In nature, iron can be either metallic ($\ce{Fe^0}$), ferrous ($\ce{Fe^2+}$) or ferric ($\ce{Fe^3+}$). In hematite, all of the iron is ferric: $\ce{Fe^3+_2O3}$. In magnetite, it is a combination of ...
• 22.8k
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### What is serpentinization, in the context of disappearance of surface water on Mars?

does serpentinization just refer to the formation of some hydrated minerals that happen to be of a class that is historically been referred to as serpentinite or it's subgroup Yes. In simple terms, ...
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### How can the 'crystal cleavage' of apatite have a four-digit number?

This is not a four- digit number but four separare numbers called Bravais-Miller indices. Bravais-Miller indices descrive the orientation of a crystal plane relative to the symmetry axes of a crystal,...
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### Why is silver found mainly in lead

This may not be a complete answer, but a big misconception here may be that silver is found "in" lead. It would be more correct to say that silver is more concentrated in the lead ore ...
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### The different types of plagioclase

I'd like to add to @SabreTooth correct answer and add the following: Plagioclase in nature commonly has a K-feldspar component: $\ce{KAlSi3O8}$. So a plagioclase crystal may be 48% anorthite, 48% ...
• 22.8k
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### Acidity of rock

According the website http://www.tulane.edu/~sanelson/eens212/igrockclassif.htm from Tulane University silica content in igneous rock is based on mass. Below is copy of the relevant part of the web ...
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### Why do gold deposits form only in certain areas of the earth?

Gold has primary origin in hydrothermal veins and contact metamorphic deposits and pegmatites. Also occurs in placer deposits of secondary origin. It is more easily found in veins that is related ...
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### Muscovite with pleochroic halos?

It's biotite. Not muscovite. That's why you have the pleochroic halos in it. I don't understand why you are saying that the interference colours are like muscovite. First of all, the lack of cleavage ...
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### What is the white coating "patina" we often see on deposited chalcedony/agate?

The white "patina" is most likely some form of opal as you suggest. I did some research and I'll explain how the agate becomes opal and why it's more common in the eroded rock. Some ...

### Are there any areas on Earth with purplish-colored soil/sand/rock/land?

Yes, there are. Here are some examples from Southern Israel: Another exceptional example is the "rainbow mountain" in Peru: The cause of these colours is the usually trace oxide amount in the soil. ...
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### Which Earth minerals would Moon colonists miss the most?

It is unlikely anything other than salt would be derived from sea water. The largest deposit of gold is dissolved within the worlds oceans - in terms of tonnes of metal. The problem with extracting ...
• 23.1k
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### Melting point of minerals

Start with my answer to this very highly related question here: https://earthscience.stackexchange.com/a/2742/725 The melting point of minerals in isolation, or a pure substance is higher than ...
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