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Questions tagged [crystals]

A solid material whose constituents, such as atoms, molecules or ions, are arranged in an highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

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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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1answer
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What kind of rock or stone is this? Where did it come from?

I found this on the side of the road in Oregon, i think it was left or forgoten about thats why it was left there but it has crystal pockets, multiple colors, some smooth sides, perfect circles and ...
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Electric permittivity of quartz

I'm performing an educational experiment on the piezoelectric effect in quartz, and it would be useful for me to know its electric permittivity. I've been told that the quartz sample that I have is ...
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1answer
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Can anyone help me identify this rock?

This is probably just something really common and boring to most people, but I was intrigued so I thought I might as well ask now I can. When I was in Portugal (I don’t know specifically where we were)...
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What type of yellow-green stone is this?

It's greenish yellow with white. Got it in a mixed stone package from Amazon. No luster, I'd say a 7 in hardness, it doesn't look homogeneous.
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1answer
51 views

is this a rose quartz

pink quartz looking stone 19 pounds found in a vehicle in new york state
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170 views

Help! Can anyone identify this deep blue rock, quartz, crystal thing from Washington?

I was like 10 waiting for my dad to get off work. He was a surveyor and brought this blue rock thing with him for me when he got off. He said they were surveying and his friend took a pickax to a rock ...
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0answers
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What is this complex reddish-brown stone with lighter spots found at a NZ beach?

I found this small stone on a beach on the east cost of the North Island in New Zealand. It's red/brown and has almost gray spots, but also has lots of white crystals coming out of it. It has a dull ...
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Help me identify these New Zealand rocks

I found these 2 at the beach on the east coast of the North Island in New Zealand. The white one is beautiful, it sparkles and glimmers and even the brown/pink veins through it sparkle, but it's ...
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1answer
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Applications of differential/integral calculus in crystallography (teaching undergraduates)?

I'm a mathematics professor who is seeking to find interesting, application-driven ways of teaching freshmen college students differential/integral calculus. I am in no way versed in crystallography ...
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What kind of stone is this? Please help!

This is a picture of a stone my friend gave to me a couple of years ago. I was wondering what it is and if it is worth anything. Thank you for your help!
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Can the formation of gypsum evaporites (sand roses) be simulated in the lab?

Has the process of formation of sand roses been simulated in laboratory conditions, or does it take too long?
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A few questions about glass

A glass, as I understand it, is a material whose solid phase is amorphous and which undergoes a glass transition when heated. My train of thought - and therefore my questions - began with obsidian. ...
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What are these crystals?

I have got a whole bunch of these crystals.
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Can someone please help identify my rock

Can somebody please help. I found this rock on the beach in the south of England. It seems to have a number of small shards of what look like crystal or glass spread around it whilst the rock itself ...
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1answer
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Is there any covalent crystals that can be easily synthesized?

I am looking for a kind of crystal that can be artificially made at relatively low temperatures (below 1500 degree Celsius) and relatively quickly (not geological time). The product is ideally ...
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1answer
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Why there are no sharp corners in nature?

I have read some articles explaining why rounded corners are more aesthetically pleasing, like this one and it all makes perfect sense but my question is: Why does nature not have sharp corners? What ...
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2answers
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Is this ice cover real - and what circumstances are required to make it?

The title says it all... I assume it requires very slow freezing sheltered from the wind. Undercooled water, maybe? A Reddit thread talks about Delaunay triangulation, but that does not explain how ...
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1answer
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What are these tumbled colored rocks?

I've been sent these rocks by a friend, but I am truly awful at identifying them because they aren't my field at all. I know some of them, but I was wondering if you could classify them all for me so ...
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What is the name for a ABC hcp lattice that is squeezed along the direction vertical to the ABC planes?

I am trying to classify a bravais lattice. It is a hexagonaly close packed lattice with (ABC) planes, that is fcc, but it is squeezed along the stacking direction, so perpendicular to the planes. Just ...
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1answer
148 views

What is the name of these crystals?

I tried searching for matching crystals online, my guess is Bournonite. What crystals are these? This image was taken by a relative at some sort of museum. The image and the observation that they ...
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1answer
494 views

Why does halite have perfect cleavage at the (110) plane?

Why doesn't it cleave nicely along the (100) or (010) or any other planes? What determines its cleavage plane? I know it has something to do with the fact that it crystallizes in face centered cubic ...
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1answer
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What kind of minerals have no cleavage plane?

Why does quartz have no cleavage plane and halite does? What do I need to know about the specific mineral so that I can decide whether it has cleavage or not? I need some kind of rule.
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2answers
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Why are there no crystals with 5-fold symmetry?

They say you can't pack objects like pentagons or octagons such that they fill up space entirely and that that's one reason there is no 5-fold or 8-fold rotational axis. Are you telling me you can ...
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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 ...
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3answers
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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 ...
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Why do crystals, like quartz and diamonds, form in different colors?

Some crystals, like quartz and diamonds, form in a variety of different colors. For example, quartz can be clear, 'foggy', pink, yellow, and even blue. What happens during the crystal's formation to ...