Questions tagged [crystals]

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

Filter by
Sorted by
Tagged with
0
votes
1answer
21 views

What California crystal/mineral is this? Is there a name for this type of crystal formation [closed]

I have a number of pieces of this very thin, flat, rock with olive green crystal in it (for lack of a more educated example) peanut brittle like structure. It's very light weight. None of the pieces ...
0
votes
0answers
20 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), ...
0
votes
2answers
81 views

Is this olivine? [on hold]

Could this small rock be olivine? It has got a rough feeling surface, and 'it's heavy. I found this in Wales 12 years ago.
0
votes
3answers
60 views

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 ...
1
vote
2answers
39 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....
3
votes
1answer
197 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?
5
votes
1answer
100 views

Does Xenon really covalently bond to oxygen within quartz?

Wikipedia's Xenon; occurrence and production says Within the Solar System, the nucleon fraction of xenon is $1.56 \times 10^{-8}$, for an abundance of approximately one part in 630 thousand of the ...
2
votes
1answer
70 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
0answers
26 views

Crystallography: The shape of axial divergent profiles

I don't know if crystallography related topics go into this stack exchange, so sorry if that's wrong here. My question concerns the characteristic shape of axial divergent powder patterns. According ...
0
votes
1answer
50 views

What type of crystal is this? [closed]

I feel like it's clear quartz that had been ripped from a cluster. However, I haven't seen this before, so I'm not sure. Can anyone confirm or correct me?
2
votes
1answer
62 views

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. >...
1
vote
1answer
57 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 ...
0
votes
1answer
82 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 ...
1
vote
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
3
votes
1answer
72 views

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 ...
1
vote
0answers
24 views

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 ...
0
votes
1answer
83 views

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)...
0
votes
2answers
93 views

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.
1
vote
1answer
78 views

is this a rose quartz

pink quartz looking stone 19 pounds found in a vehicle in new york state
3
votes
3answers
637 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 ...
5
votes
2answers
345 views

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 ...
1
vote
1answer
314 views

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 ...
4
votes
1answer
309 views

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 ...
0
votes
1answer
258 views

What kind of stone is this? Please help! [closed]

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!
4
votes
1answer
63 views

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?
3
votes
2answers
253 views

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. ...
4
votes
2answers
125 views

What are these crystals?

I have got a whole bunch of these crystals.
4
votes
3answers
3k views

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 ...
0
votes
1answer
41 views

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 ...
1
vote
1answer
691 views

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 ...
18
votes
2answers
559 views

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 ...
5
votes
1answer
229 views

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 ...
3
votes
0answers
40 views

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 ...
5
votes
1answer
157 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 ...
12
votes
1answer
591 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 ...
10
votes
1answer
3k views

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.
6
votes
2answers
13k views

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 ...
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.
15
votes
2answers
14k 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 ...
13
votes
3answers
4k 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 ...
21
votes
2answers
13k views

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 ...