Questions tagged [minerals]

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4
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1answer
40 views

Is there any mineral that survives hard degree metamorphism?

When a protolith enters in metamorphism, the minerals transform in other new stable minerals while the pressure and/or temperature increase. Is there any mineral that would not be affected by a high ...
1
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1answer
72 views

How to genetically classify a weathering mineral or a mineral formed in soil?

Coming from this question and the answer, a proposed genetic classification of minerals: Endogenic: Magmatic, Metamorphic, Hydrothermal. Exogenic: Supergene, Sedimentary. My question is how would ...
3
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1answer
53 views

What questions to ask to students from a mineral guide dataset?

I am programming an app that consist in 180 mineral sheets of interest for geology students. My database have the following fileds: Identifier Name Name 2 Type Class Formula System Environment1 ...
5
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2answers
193 views

Is this classification of mineral formation environments correct?

I am writing an app for students that consist in 180 sheets of the most common minerals on Earth's Crust. One of the fields of the sheets is environment of formation. It is important to me to ...
4
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1answer
32 views

Why is Melanterite white or colorless?

I've read that melanterite (FeSO4*7H2O) is colorless or white and gets to be green to blue with increase in Cu2+ impurities. But from my chemistry experience I know that iron sulfate is green when in ...
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1answer
23 views

"Down wash" as a source for mineral particles in the soil

In a previous IGCSE examination paper$^1$, the following question was asked and answer provided: State one source of mineral particles in soil. Marking Scheme: Accept any one of: rock; down wash; ...
3
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0answers
23 views

Can geochemical anomalies of stream sediment samples be used directly for mapping targets?

We know that geochemical dispersion in stream sediment is much widespread, facilitating discovering mineral targets in a regional scale. However, we also know that there should be discrepancy in space ...
2
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1answer
138 views

Are there any sulphides, sulphates, carbonates that cannot be dissolved by aqua regia?

I was looking into these specific minerals: arsenopyrite, pyrite, chalcopyrite, barite, calcite, dolomite. I investigate issues with tellurides not showing expected gold concentrations. There is gold ...
5
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2answers
654 views

Mining iron or metals in nature

Upon watching all the videos from PrimitiveTechnology on Youtube, I've decided I would try something similar. I know how to make clay and use this to make an oven. I also know how to make charcoal. ...
7
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1answer
2k views

How do hematite and magnetite form?

I want to understand the conditions under which hematite $\ce{Fe_2O_3}$ and magnetite $\ce{Fe_3O_4}$ form in nature. The linked Wikipedia articles explain various conditions under which they form, but ...
4
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2answers
149 views

Are there minerals that can't scratch each other but have different hardness on Mohs scale?

So I was reading here that Mohs scale is not transitive and therefore could not overcome the comparative phase in order to be turned into a measurement procedure. As it is written in the webpage, &...
4
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2answers
118 views

Database of mineral with images for a neural network application

I'm diving into data science and I'm looking for a complete database of minerals. I downloaded the csv file from http://rruff.info/ima/ . It contains 5516 lines of data but it does not have images or ...
16
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3answers
28k views

How do geologists find ore deposits?

From my research, there is lots of information on how to extract ore, but I can't find any information on how these ore deposits are found in the first place, apart from 'looking for surface ...
14
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3answers
6k views

How and where do double-terminated crystals form?

How and where do double-terminated crystals form? Most terminated crystals form by 'growing' out of a rock. Which causes one side to be flat,(or whatever the shape of the rock it 'grew' out of was ...
22
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3answers
22k views

Where can obsidian be found?

Where is obsidian found? Is it typically found on the surface or underground? If underground, how far under (meters or feet would be perfect)? Also, is it found everywhere on Earth, or just in areas ...
2
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1answer
82 views

Term for the Process of the Early Earth's Crust's Changing Mineral Composition

In the book, Story of Earth-The First 4.5 Billion Years, From Stardust to Living Planet, by Robert Hazen, Chapter 3: He discusses the changing mineral composition of the early Earth's crust from ...
2
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1answer
118 views

Avoiding fake trinitite

I would like to get some trinitite for my rock and mineral collection. The problem is that there is apparently a lot of fake trinitite for sale in the internet. How do I avoid the fakes, and be sure I ...
2
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1answer
59 views

How to identify chemical property and structure of rocks?

I am interested in identifying the properties of rocks. For example, black opal is shiny and can emit 5 different colors based on different lighting conditions. Is there a way for an amateur to be ...
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0answers
24 views

Ore prospecting and the low-hanging fruit effect

I'm trying to acquire an understanding of how the difficulty of prospecting for useful ore has increased over historical timescales. Intuitively, I would expect that centuries or millennia ago, you ...
1
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1answer
51 views

Ore Deposit Identification

What type of ore deposit does this rock best represent? A rock with a porphyritic texture is cross cut by a stockwork of quartz veins. Bordering the veins is extensive alteration of the host rock. ...
3
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1answer
237 views

Cleavage of minerals

What is the difference between 3-dimensional cleavage and cubic cleavage? I think, they are the same, but I am not sure about if I was right or not.
1
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1answer
60 views

What causes dye to bleed from an agate stone?

I came across this review on Amazon. The cold drink was placed on top of the agate stone and the dye bled and left a permanent mark on the table. Why does this happen? Is it because of the ...
3
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1answer
78 views

How can the 'crystal cleavage' of apatite have a four-digit number?

On Wikipedia's page for apatite, the crystal cleavage is listed as [0001] or [0101], which I assume are Miller indices.... But how can there be four numbers/digits instead of two, like there usually ...
4
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4answers
100 views

How is it possible for rocks to be trapped within another type of rock?

More specifically, I would like to know how the rocks in these pictures have formed: If this is because magma has melted and trapped the other rocks inside, do they have a different melting point ...
3
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0answers
28 views

Looking for videos/GIFs of petrification/permineralization

Do you know of any good animations, videos, or GIFs of petrification/permineralization? For some students verbal and written explanations don’t work, they don't always visualize well. So it’d be ...
0
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1answer
156 views

Have fossils ever been found in the asphalt lakes of Trinidad and Venezuela?

La Brea tar pits in California are the result of ancient oil seepages and famous for the fossils of extinct animals which were trapped in the tar. The asphalt lakes in Trinidad and Venezuela are also ...
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2answers
164 views

How to genetically classify a mineral resulted from weathering?

I am writing a mineral guide for smartphones which classifies minerals according to their formation environment. From sugestions on this related question, I changed the classification to: ...
4
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1answer
104 views

History of the Arctic Ocean

Much of the Arctic Ocean is fairly shallow compared to other oceans. There must have been times in the past during severe ice ages that a lot of what is now the ocean bed was above sea level. When was ...
6
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2answers
227 views

Can I just walk around Greenland with a UV light and find rare Earth minerals on the ground?

The NPR.org news article and podcast Greenland Is Not For Sale. But It Has The Rare Earth Minerals America Wants is interesting, and it includes a few large GIFs (too large to post here) that appear ...
3
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1answer
51 views

Hyperspectral Detection of Ore

How can I use hyperspectral satellite imagery to remotely detect copper or any prespecified mineral deposit in general? Where can I find a database of the absorption and reflection bands of various ...
2
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1answer
191 views

Is there any mineral identification techniques that works for all minerals?

Are there any mineral identification techniques that work for all minerals(non-metallic/metallic), so that an electronic device could be made to distinguish between all minerals?
5
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2answers
386 views

Muscovite with pleochroic halos?

Is it possible to find pleochroic halos in muscovite ? I would have said that it must be biotite (also, in PPL it is brown!), but then.. why does it have interference colors so similar to muscovite ? ...
3
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1answer
276 views

Differentiate a rock and mineral

How to differentiate between a rock and a mineral by merely looking at it as a thumb rule?
5
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1answer
144 views

Strange coating in old lime mine shaft

Near Prague,Czech Republic is old lime mine. Most of it is closed but one short transport tunnel under one hill is publicly accessible. Tunnel has profile around 2,5x2,5m and it's slightly bended and ...
5
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1answer
252 views

What are the cubic formations found inside Larimar gemstones?

I recently noticed what appears to be common cubic formations just beneath the surface of Pectolite (Larimar) gemstones. They quite resemble transparent sugar sprinkles. Each formation isn't perfectly ...
17
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5answers
32k views

Why do gold deposits form only in certain areas of the earth?

In the map above you can find that most elements are spread evenly throughout Earth's crust and that they are available all around the Earth. However, gold can only be found in certain areas of the ...
3
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2answers
3k views

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

This sort of comes from my related question, but only sort of. Are there any areas on Earth with purplish-colored soil? The purple tint would come from some mineral, perhaps deposited by rivers or ...
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2answers
89 views

Chloride ions for the salty seawater

Where does the chloride ions that are required for the salty taste of sea water come from ? I know that it is the weathering caused by the slightly acidic (due to dissolution of CO2 with water) rain ...
16
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2answers
19k views

Why does the colour of amethyst fade if exposed to too much light?

It is well known that the purple hue that is characteristic of the amethyst quartz ($\ce{SiO2}$) will fade if the crystal is exposed to light for a prolonged period of time. What is the underlying ...
17
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2answers
16k views

What determines a mineral's hardness?

Mohs Hardness Scale is basically a measurement of the hardness of a material, or more specific, a rock or mineral. But I have never been able to figure out why some minerals are harder than others.
3
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1answer
2k views

What's the difference between cleavage and fracture?

I see both terms refereing to fractures on crystals or minerals, so I wonder if they could be considered synonymous. If no, what's the difference between both terms?
2
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1answer
189 views

An oblique-square-prism crystal?

Does any mineral crystallize in the shape of an oblique square prism? If so, what crystal system (monoclinic, cubic, hexagonal, etc.) would such a mineral fall under?
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0answers
13 views

Why do allophane soils behave as gels?

It is notoriously difficult to determine the texture of soil containing allophane and immogolite. According to the literature this is because the clay fraction "behaves as a gel", i.e. it's not ...
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2answers
652 views

How are minerals classified?

What exactly is done to classify minerals in Earth Sciences such as Geology? How can it be known if one mineral is the same as another if they should be visually different?
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1answer
197 views

What is cluster situation with respect to sand mining?

Guideline on handling cluster issues : The original Environmental Impact Assessment ( EIA ) notification does not provide for the procedure to handle cluster situation, which has been proposed in ...
2
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1answer
357 views

How salty can snow/sleet be?

Can enough salt particulates be in the air to create salty snow or ice that is undrinkable? Will ice form in sub zero temperatures through condensation in salty air?
3
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1answer
329 views

Preservation of clay items

I have a general question which may sound naive: archeologists eg in Ancient Greece take a lot of information from preserved pottery they found. What physical attributes of ceramic items made of clay ...
2
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1answer
131 views

Where to start searching to find more radioactive minerals?

I'm pretty new to all this... I've recently purchased a Geiger counter, and am hoping to locate rocks like pitchblende and other radioactive minerals for my collection. I'm based in the North West ...
0
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1answer
127 views

I need help with these geode like rocks [closed]

I found these rocks in my pasture and was excited because I thought I had found some geodes. The rocks were in a sandy bank and looked like eggs sticking out of the bank. I am located in Ness County ...
5
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1answer
543 views

How does palingenetic fusion occur in rock?

As far as charnockites are concerned, granitic charnockites are formed due to palingenetic fusion and metasomatism, while granulitic charnockites are formed due to high grade metamorphism. When I ...