Questions tagged [mineralogy]

questions relating to the scientific study and identification of minerals.

Filter by
Sorted by
Tagged with
2
votes
2answers
85 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 ...
3
votes
1answer
62 views

“Obicular” structures in basalts

I found spherical or globular structures, structures in basalts of a greenstone belt which underwent alteration and deformation. However, in thin section, these structures have undeformed pyroxene and ...
5
votes
1answer
57 views

Does muscovite occur as a contact metamorphism mineral?

Does muscovite occur as a contact metamorphism mineral, with dacitic intrusion into dacitic rocks?
0
votes
0answers
23 views

How to prepare sulfur crystal specimens?

I mined sulfur crystals last week and I read the following on this guide: To prepare the specimens [...] it is necessary to soak them in water to which ammonium hydroxide has been added. This ...
1
vote
2answers
75 views

Where can I get mineral testing done? [closed]

Where can I send a sample of material to be tested to see exactly what it is? Do you have an address where items can be sent for testing and evaluation? I have a softball size rock that was given to ...
2
votes
1answer
172 views

What are these features in the Tombouctou Region?

I’ve recently been very interested in globe-trotting via Google Earth. At first I was using it to plan out hikes to possible mineral deposits locally, or potential fossils/ archeology sites. However I ...
2
votes
1answer
155 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
votes
2answers
283 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
votes
1answer
181 views

Differentiate a rock and mineral

How to differentiate between a rock and a mineral by merely looking at it as a thumb rule?
4
votes
1answer
177 views

Why would CaO be more finely spread than K2O in Granodiorite?

I recently interpreted some XRF data on samples of a granodiorite which were classified under three different types of physical characteristics: very little, mild and significant levels of weathering. ...
5
votes
1answer
124 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
votes
1answer
162 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 ...
12
votes
5answers
18k 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
votes
2answers
2k 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 ...
2
votes
1answer
38 views

Name of majorite endmember $\ce{Mg3(FeSi)Si3O12}$

Does the majorite garnet $\ce{Mg3(FeSi)Si3O12}$ have a name?
4
votes
1answer
1k views

Does ground-to-cloud lightning create crystals as well?

I've read that cloud-to-ground lightning can create fulgurites. Does ground-to-cloud lightning also create crystals within the earth as it surges through the minerals?
1
vote
1answer
76 views

Rock ID: black rock found in Central Europe [closed]

I'm note sure if it's an anthracite, augite, jet (lignite) or something completely different. I don't know where exactly i found it because it's from my old rock collection. I would appreciate your ...
0
votes
1answer
122 views

Identification required, rock formation found whilst on holiday in Cephalonia, Greece white object embedded inside? [closed]

This rock was found in kephalonia Greece, on a beach in lassi. The rock is black in colour, smooth with thumb like prints, very metallic smell and very slightly magnetic. We took this rock to oxford ...
18
votes
1answer
2k views

What are these metallic nodules that were found at low tide on the UK south coast? [closed]

Smooth spherical crystalline metal nodules Outside and inside surface does not scratch with a knife blade Inside lustre brassy, radially striated metallic crystals radiating from a lumpy centre at the ...
1
vote
4answers
529 views

What is this Lake Michigan rock? [closed]

Rock found along northern Lake Michigan, (Charlevoix, MI). Made up of very thin crystalline layers. There are small, round bubble like bumps that protrude from the surface. Doesn't show well in the ...
0
votes
0answers
23 views

Space Symmetry Groups: Wyckoff notation, diagram and positions

In the subject: "Introduction to Chemical Geology", I have given the spatial symmetry groups. At present, I know the different symmetry operators: rotation axes, center of symmetry (or inversion), ...
1
vote
3answers
88 views

Pinkish rock with red 'veins' [closed]

I found this rock in Smithfield NC. It does scratch glass. A butter knife didn’t scratch it. When you hold it to a light it has an orange glow. It didn’t leave anything on porcelain.
8
votes
2answers
2k views

What is this blue rock? [closed]

I am trying to identify a rock my husband found.The rock was found in Columbus Ohio about 20 feet (6 m) down. It is about the size of a basketball and extremely heavy (90 lbs) and difficult to cut ...
2
votes
0answers
210 views

Green Rock Identification [closed]

This rock was found in the highlands of Scotland in the mountains.It is 2 1/2''x2 1/8''x 1'' it has a density of 2.95 leaves a clear streak weighs 130 grams and a hardness of 6 on Moh's scale.This ...
3
votes
1answer
309 views

Is this rock Massive Epidote? [closed]

enter image description here This is a close up of outside of chipped off piece, and inside alsoI found this rock in Co. Donegal Ireland on a river bank buired under the dirt. It weighs 16.4lbs- 7....
3
votes
2answers
35 views

Database of color wavelengths of minerals

I was wondering about the physics of color, and now am interested in finding out if there are any resources (databases, text files, html tables, or pdf listings) of minerals and their associated ...
0
votes
1answer
38 views

UK Mineral identification help [closed]

Can anyone help me identify these minerals please? I found them on a beach in northern England. The first has tiny angular crystals, some slightly pinkish maybe in certain lighting conditions but grey ...
1
vote
0answers
52 views

what type of rock is this? blue/green and brown [closed]

I found this rock while up in the mountains and I have no idea what type of rock it is.
15
votes
2answers
15k 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
votes
2answers
13k 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.
20
votes
2answers
2k views

In what geological situations can I find gold?

I've heard that gold ore is often associated with quartz veins. What geological processes enable gold particles to naturally cluster together like this? What characteristics/properties should I look ...
22
votes
2answers
1k views

Peak phosphorus - what are the sinks?

The minable phosphorus reserves are limited. Where is the mined phosphoprus landing, what are the global phosphorus sinks? I would assume that most phosphorus is used for fertilizer and ultimately ...
1
vote
2answers
41 views

What does the unit cell of petitjeanite look like?

The question in Chemistry SE What is the crystal structure of bismuth oxyhydroxyphosphate (BOHP)? is about a catalyst synthesized by accident. A link in this comment points to the page https://www....
5
votes
0answers
64 views

Chloride and evaporation

I have a layered aquifer with water that contains high concentrations of calcium and sulfate (~400 mg/L Ca2+, ~1300 mg/L SO42-), at 50 cm below ground surface (bgs), 250 cm bgs and 300 cm bgs. The ...
3
votes
1answer
580 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
votes
1answer
71 views

What is this translucent and blue vein crystal, 7.5 < Mohs < 9, Lustre: Aventurescence [closed]

It looks like quartz, but it has blue veins on the surface that look died. Not all surface scratches are blue though. Hardness: > 6.5. Nail file will not scratch it. > 7 quartz will not scratch it. >...
2
votes
1answer
92 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?
1
vote
2answers
48 views

Can gemstones be cut into sheets? [closed]

TL;DR: Without lasers, electricity, or otherwise modern tools, could large transparent gems be sliced (like glass window)? So I’m world building. On this planet they have caves with enormous gemstone/...
1
vote
1answer
18 views

Does the shear modulus of silicate minerals vary significantly with changes in P and T?

I know that the bulk modulus, K, varies with pressure and temperature for silicate minerals and liquids, but what about the shear modulus? If so, is the change drastic for changes from standard ...
0
votes
2answers
70 views

Phase relation for mantle?

I have information about temperature, pressure, normal and shear stresses, viscosity, conductivity, density, heat capacity and adiabatic heating for a particular area of mantle in the form of 2D ...
0
votes
1answer
49 views

Is this an agate? [closed]

So I have found these in a creek there are some that look like this and I have broke them open and they were full of crystals these seem to small and I have tried cracking then and they wont budge I ...
1
vote
2answers
217 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?
2
votes
1answer
83 views

Metallic Balls Found in Sandstone or Mudstone Layer [closed]

Found metallic balls of some type of metal ore surrounded by yellow mudstone the metallic balls crush easily into a fine gray powder. The gray balls are situated between sandstone layers in a soft ...
1
vote
1answer
85 views

Mineral/rock identification [closed]

I found this rock in the Himalayan region in India. It was on the roadside of a hill that we were trekking. It has a silver lustre. It has a hardness of 5.5(I can scratch it with a knife blade).it has ...
4
votes
1answer
83 views

Can someone identify this mineral? [closed]

I found this in a stream in Medicine Bow-Routt National Forest, Wyoming. One side (2/3 length) has a pointy pyramid with four faces; other side (1/3 length) has four faces but with with an edge ...
1
vote
1answer
120 views

Mineral identification - please help!

I'm currently writing an essay on a mosaic in the British Museum, and am unsure about which stone the frame is constructed from (pictured). I would be most grateful for help identifying it. Thanks! ...
1
vote
1answer
61 views

What is this translucent blue-green oblong crystal? [closed]

I think it might be aventurine of some sort, but I'm not sure. Hardness: It is harder than a steel nail file. The file leaves a track, but it rubs off, leaving no mark. I scraped it on the bottom ...
2
votes
1answer
90 views

Where/how people find minerals

Forever I have seen little shops here and there offer minerals like those crystals and neat shaped rocks of different kinds, turquoise and amethyst and many others and such. But I never really thought ...
3
votes
1answer
81 views

Do Pyroelectric gemstones really exist? Can they be found on web market?

I just got the curiosity today to know whether the gems that produce electricity non stop without an end exist, and I have found this site. But I’m having doubts about it, thinking that it could be ...