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Questions tagged [mineralogy]

questions relating to the scientific study and identification of minerals.

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Green Rock Identification

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 ...
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What kind of red rock is this?

I don’t know much about were I live, I am from ny and only moved here a few years ago. I found it in Smithfield nc we’re I love with my dad and kids now.. I wish I had more information. Yes the rock ...
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Pinkish rock with red 'veins'

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.
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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 ...
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Is this rock Massive Epidote?

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

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 ...
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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....
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146 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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41 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/...
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Name of majorite endmember $\ce{Mg3(FeSi)Si3O12}$

Does the majorite garnet $\ce{Mg3(FeSi)Si3O12}$ have a name?
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1answer
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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 ...
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1answer
58 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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45 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 ...
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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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Metallic Balls Found in Sandstone or Mudstone Layer

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 ...
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What kind of efflorecence is this?

It occures in a tunnel under tens of meters of vulcanic deposits (mostly Thephra i think) at Herculaneum, Italy. Water seems to come from the surface, however the sea is near. It's level is lower ...
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1answer
59 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 ...
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78 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 ...
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1answer
113 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! ...
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What is this translucent and blue vein crystal, 7.5 < Mohs < 9, Lustre: Aventurescence

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. >...
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1answer
54 views

What is this translucent blue-green oblong crystal?

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 ...
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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 ...
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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 ...
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If the study of “minerals” is covered by inorganic chemistry

I am wondering what field studies "minerals", such as the minerals in Wikipedia's list. I keep thinking that perhaps it would be covered in inorganic chemistry (list of inorganic compounds wiki), but ...
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Why would India have so much thorium on it's beaches?

The recent BBC News article Why India Wants to Turn it's Beaches into Nuclear Fuel includes the passage: The tropical beaches of India probably bring to mind sun-dappled palms, fiery fish curries ...
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I found this strange spherical stone in Gillette Wyoming. I have no idea what it is. Please help.

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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1answer
79 views

Is this a rock with metal or gold? [closed]

I found these really hard rock while i was excavating. It caught my attention the different colors.
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1answer
63 views

What kind of purple stone is this?

I found this stone and I do not know what type of stone is this?
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59 views

Help Identifying this Mineral? [closed]

I have the following rock/mineral but can't seem to identify. Anybody have an idea what it might be? It's heavy, 3"x3", nonmagnetic (but slightly repels a neodymium magnet), blackish in color with ...
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1answer
71 views

Please identify- no origin known but given to me by a geologist

A very dear man who love his job as a geologist gave this to me. He’s been all over the country so I have no idea where he may have picked it up
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52 views

What is this Stone [closed]

I found this stone in my father's old stuff. I tried to search online for about it but I don't know what is it. It looks to be a rare stone. Can someone identify it?
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1answer
221 views

heavy, brown, rock with crystals, please help identify

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 ...
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A chemical formation or constructed by microorganisms?

This mineral formation was at the side of a fresh water canal in Gürpınar, Van, Turkey. It was dug out from the bottom of the canal. It is very brittle. I know that the natural water sources in the ...
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63 views

What are the name of these stones?

There are some kind of stone, I collected them and I want to be sure of their identification.
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134 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 ...
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Is this petrified wood or just “some rock”?

I was gifted this and have no idea what it is and was to embarrassed to ask, so here I am.
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57 views

Can you help me identify my rock?

I found this rock in my yard. Can someone please identify it for me? I’m not sure if you can see the blue hue on the rock in the picture! (https://i.stack.imgur.com/cuklH.jpg)
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How does chalcedony containing quarts and mogánite form?

I just learned that the cryptocrystalline form of silica, chalcedony, usually contains 1-20% of the monoclinic $\ce{SiO_2}$ mineral mogánite as well as the much more common hexagonal quartz. With time ...
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1answer
63 views

Unidentified mineral found in France

(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-...
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1answer
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Are these obsidian snowflakes?

I'm not sure if these are obsidian snowflakes: I found it near a river, hardness is 4 to 5, it has a wax lustre when pre-polished. The 'flakes' in the matrix are raised and gray. Pre-polished side ...
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1answer
151 views

What exactly are enantiotropic and monotropic polymorphic transitions?

Recently, I've been studying the subject of polymorphism and met two important concepts, the monotropic and enantiotropic polymorphic transition types. However, I can't really seem to grasp the ...
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1answer
107 views

What's this? Chess pieces growing spines!

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 ...
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1answer
147 views

Is this deep green calcite, green gneiss stone?

The site where it is found is characterized by schist, quartz and gneis, but also other species of rock. This is a scissors 2 cm semi transparent, vitreous luster, hard scale 6.5 - 7 ... I will post ...
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1answer
87 views

What is the type of stone/mineral in this necklace please?

I would like to sell this necklace but can't remember its original description and the online store where I got it no longer carries it so I can't look it up that way. Blue Chalcedony comes to mind, ...
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1answer
162 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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1answer
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Can you help me identifying this beige/brown rock?

I found this stone in a box where I keep some memorabilia. Unfortunately I don't know, where it's from, maybe it's from a mountain side in the alpins or from a beach at the mediterranean sea. One side ...
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1answer
127 views

Help identify this brown red mineral?

This was found in my garden today and has me completely stumped. What is it?