Questions tagged [mineralogy]

questions relating to the scientific study and identification of minerals.

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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
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1answer
350 views

What kind of light blue stone is this? [closed]

My son found this stone on the beach on the island Crete. It was a one of its kind, no other visible stone on the beach was the same. We asked the locals, but they did not know this stone. It's about ...
5
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1answer
197 views

Difference between pyrite oxidation and dissolution

I've seen papers use oxidation and dissolution of pyrite. Are these two processes the same? I was always under the impression that pyrite does not dissolve easily. What is the difference between ...
5
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1answer
457 views

Icelandic rock I am trying to identify [closed]

This is a rock that I picked up from underneath a melted segment of Glacier in east Iceland. It is not unusually heavy or light for it's size. I can scratch the surface away with a penny. The ...
5
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2answers
73 views

Sulfate salts of magnesium and sodium

What concentrations of magnesium, sodium and sulfate are needed to precipitate solid MgSO4 and Na2SO4 (let's say evaporation is occurring in a system) I'm assuming probably really high because they ...
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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 ...
4
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1answer
796 views

What are the implications of the recent discovery that huge oceans exist close to the mantle of the Earth? [duplicate]

I was of the notion that as we get deeper into the Earth, it gets hotter and hotter. If so, how can there be huge oceans (they seem bigger than our Pacific) exist at such a place? If so, what are the ...
4
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3answers
781 views

What kind of rock or mineral is this? [closed]

I found this rock or mineral in our backyard, and I'm having a hard time trying to figure it out. Does anyone know exactly what this thing is
4
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1answer
70 views

Unidentified mineral found in France [closed]

(I am not a native english speaker, so I'm not really aware of the specific terminology.) A few years back, I found an unidentified rock on a beach in Normandie (France). It looks and feels (texture-...
4
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1answer
206 views

What type of gem is this? [closed]

I was wondering what type of stone this is. I tested it on Mohs hardness scale. It scratched quartz. I found it at Crystal Cave in Kutztown, Pennsylvania. They were selling bags of gems you could sift ...
4
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1answer
253 views

A sedimentary rock with only minerals

In my text book I came across this multiple-choice question A sedimentary rock consists of only minerals and lacks fossils, it could be classified as: i) a clastic sedimentary rock ii) a ...
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2answers
127 views

What are these crystals? [closed]

I have got a whole bunch of these crystals.
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1answer
1k views

How can I normalize this chemical analysis to a mineral with 3 cations?

$\ce{FeO}$ = 70 wt% $\ce{TiO2}$ = 30 wt% The molecular weight given of $\ce{FeO}$ = 72, and the mw of $\ce{TiO2}$ = 80. The first step I did was divide each wt% by their molecular weights to get a ...
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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?
4
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1answer
140 views

Online resources for geographical distribution of minerals

I'm trying to find the geographical distribution and availability of mineral Brannerite. Is there a resource online to know or query where a certain mineral is found? On the link page, they mention ...
4
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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 ...
4
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1answer
113 views

What's this? Chess pieces growing spines! [closed]

These chess pieces have laid undisturbed for a long time (15-20 years?). In this time, they seem to have grown clear/white, spiny, long crystals. I'm wondering if they are dangerous, but also curious ...
4
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2answers
453 views

Can someone identify this rock with fibrous white veins [closed]

What is this I found this in my back yard im unsure as to what it is and would really like to know.
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2answers
433 views

Looking for a complete table of minerals for a database

I am building an open source spatial geochemical/geological observational database for mineral exploration. I need to fill the mineral lookup table. Where can I find a complete list of all minerals ...
4
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2answers
137 views

Please help identify this! Rock? Glass? Crystal? It's big and very heavy [closed]

About 1.5 feet tall, 1 foot deep and 2 foot wide. Very heavy and very hard. I will get a better picture posted asap. You can read a newspaper thru it. Was left to me by my uncle years ago but never ...
4
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1answer
54 views

Is there a table with decomposition temperatures of common minerals?

I am about to perform a Loss On Ignition test on a material I know that contains among on things kaolinite, which will release water at 500 $^oC$. However, I tried finding a table with decomposition ...
4
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1answer
68 views

Is a controlled fractional crystallization process feasible on the Moon?

I am looking for a way to separate metal oxides on the Moon. Please bear with me - it's for an ultra-hard science fiction project. Processes typical on Earth are not effective there. Heat is cheap on ...
4
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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. ...
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608 views

Could this be pyroxene twinning ? (thin section)

I found this beautiful euhedral pyroxene crystal in thin section today. There is one thing that I can´t explain though. In crossed polarizers, the crystal shows two different interference colors, ...
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406 views

I have found this structure in thin section. What is it?

I have been observing a nepheline specimen under polarized light and found some interesting places. I have taken several images. The first shows a micro-geode with parallel polarizers, second with ...
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28 views

Can humidity changes induce stacking-sequence changes?

My understanding is that some minerals with layered crystal structures will reversibly absorb water with changes in humidity. Are there any minerals where this reversible absorption leads to a ...
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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 ...
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2answers
289 views

I found this strange spherical stone in Gillette Wyoming. I have no idea what it is. Please help. [closed]

These are recent pictures of it. It’s heavy, I see small minerals that catch the light in it, very bumpy, spherical, doesn’t seem to be magnetic, I was falling down a deep trench and kicked it up at ...
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2answers
179 views

Help identify glowing stone with scarab carving [closed]

I found almost no information from searching Google, Someone mentioned it might be Fluorite. I simply don't know where else to look for an answer and so I am asking you. When I was a child, my ...
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1answer
562 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?
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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 ...
3
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1answer
611 views

Is porphyritic texture always indicative of a 2 stage cooling process?

Is porphyritic texture always indicative of a 2 stage cooling process? Can't the phenocrysts and groundmass be formed at the same time depending upon the chemical constituents forming the rock? The ...
3
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1answer
179 views

Differentiate a rock and mineral

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

The influence of special emissions (possibly coal mining activity) on particulate matters

Based on multiple site sampling of airborne $PM_{2.5}$ and $PM_{10}$ , the elemental concentrations of the trace elements were analyzed. I have found out in the site near surface coal mining zone ...
3
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2answers
129 views

Why do buoyantly rising mantle minerals melt, yet buoyantly rising atmospheric waters condense?

In the mantle, minerals contained in buoyant plumes of rock undergo phase changes from solid to liquid (decompression melting). In the atmosphere, waters contained in buoyant plumes of air undergo ...
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1answer
705 views

What is the difference between mineral groups and series?

It seems to me when reading about minerals, groups and series are spoken about interchangably in similar types of contexts. Is there a difference? If so, what?
3
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1answer
410 views

Significance of crystal classes in crystallography

I am studying crystals and I learned that there are 32 crystal classes with well-described data regarding symmetries. I have visited a few sites and am having difficulty determining the significance ...
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2answers
34 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 ...
3
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1answer
403 views

Identification of mineral [closed]

I recently visited a quarry site and brought home a rock sample that had two clusters of cubic crystals on its surface. I am unsure what the mineral is, I think it may be fluorite but I am not certain....
3
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1answer
90 views

How do cations control the crystal structure of silicate minerals?

Beyond the obvious fact that in many of the silicate subtypes they play an ionic 'glue' like role by bonding the tetrahedra units together; how do cations control the structure of a silicate and how ...
3
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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
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1answer
294 views

heavy, brown, rock with crystals, please help identify [closed]

please help identify this rock. it is heavier than most. dark brown color. picture is shown with streak test. found in Philadelphia pa. at home demolition site. crystals seem to be different type and ...
3
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2answers
84 views

Iron-nickel phase in pallasite meteorites

I have recently been learning and researching about meteorite types and classification. Pallasites are mainly composed of a 'solid-solution' of olivine crystals and an iron-nickel alloy. My question ...
3
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1answer
486 views

Saturation Index clarification

I have a problem with my project and I was hoping I would find some clarification. I did some modeling with phreeqc to calculate saturation indices and found that calcite was saturated in an ...
3
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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 ...
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0answers
49 views

What processes cause basalt to form a columnar structure? [duplicate]

I have run across many pictures of rocks that look like almost perfectly carved columns. For example: the Twyfelfontein Organ Pipes, the Basaltic Prisms of Santa Maria Regla, and the waterfall ...
2
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3answers
406 views

Why are there craters on the moon?

The Earth's moon is in synchronous rotation around Earth. The question: Why are there craters on the lit side of the moon and the dark and of which are not parallel with crater schemes on Earth?
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2answers
1k views

Melting point of minerals

Looking at this website, I can see the melting point of the following minerals: http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/meltrock.html Apparently at a temperature of 1200 °C, all the ...
2
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3answers
800 views

Is it possible to determine where gold might be found based on a map, and if so, how? [duplicate]

Is it possible to locate potential gold deposits using maps that describe dominant rock type, altitude, vegetation, or geological formations? (I realize that the location would probably still have to ...
2
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2answers
84 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 ...