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The reason minerals like quarts and diamonds vary in color is generally caused by the chemical elements involved while the crystal is being formed. Chemicals Different colors can be created by different chemicals. Amethyst for example has traces of iron built into its crystalline structure giving it a purple hue. Iron can also give crystals a yellow hue. [...


12

Yes, it is real. Whoever took the photo, congratulations on a very fine image. I have never seen this texture on such a scale, but something similar can be achieved in the laboratory by creating a bubble membrane of pure super-cooled water and blowing a few dust nuclei onto the surface. A comparable geometry appears very rapidly. The size of the ice crystals ...


12

The premise of your question is entirely wrong. There are many examples of sharp corners in nature, the most obvious being well formed crystals. Pyrite is a classic example that was mentioned by @wienein in the comments. In a ideal situation it forms cubic crystals with sharp edges. A classic non-crystalline example would be volcanic glasses such as ...


12

The hardness of minerals is diagnostic because the hardness is determined by the strength of bonds and the structure of the mineral lattice. Hardness is basically the stress required to create and grow extended lattice defects such as micro-fractures, stress twins, and dislocations. Diamond, quartz, and framework silicates, such as feldspar, are hard ...


10

Double-terminated crystals can from by crystallizing from a melt. The crystallization nucleus has to float freely in the magma chamber. As long as no other crystals obstruct the growth the crystal will grow in its own characteristic form (euhedral). This happens for example with feldspar crystals. (Example: http://www.erdwissen.ch/wp-content/uploads/2010/12/...


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I'd like to elaborate of the Chemicals issue of Azzie Rogers' answer. You can divide the chemical coloring into three main parts (there may be more, but these are the important ones): Inclusions A large, solid crystal can have tiny inclusions of other solid minerals. Commonly these inclusions are too small to individually observe by the naked eye. ...


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This picture was taken in what seem to be a small pond, of very calm water. It seem that in ideal conditions, implying but not limited to : absence of winds clean water eg: no nuclei to provide an anchor for crystal formation low temperature gradient between air and watrer (air almost near 0 °C and very slowly falling) ice grain can grow quite large. This ...


7

The colour, crystal morphology and twinning strongly suggests rutile (titanium oxide). Please see MinDat.org (e.g. http://www.mindat.org/gallery.php?cform_is_valid=1&min=3486&cf_pager_page=36) for examples


6

All unit cells are parallel-sided hexahedra. These are six sided shapes with parallel opposite sides. Their three principle angles may or may not be 90 degrees. And the three side lengths may or may not be equal. All of these unit cells can be uniformly stacked. Using these building blocks it is only possible to produce planes of reflection, diads (axis of ...


5

It is a large block of quartz or chert, broken off from a rock called conglomerate. Your knife doesn't scratch it because quartz is harder than knives. When scraping at it my knife seems to leave a kind of silver mark, which fades when rubbed. It's as if the knife is somehow scraping off onto the rock? Basically, yea. The bronze stuff around it is ...


5

I am pretty sure that it is bulk or recycled glass. It might have been a discarded or lost piece left from previous users of the land. Glass rocks have also been used for landscaping which might fit with the discovery location. I haven't seen any natural rock with such blue and uniform coloration. At various rock stores you can find similar material, it ...


5

I'm pretty sure a more rigorous answer deserves to come along, but I can give a simple overview of some of the important factors. Cleavage planes have to do with bond strength and bond geometry. If there isn't a plane of bonds that can be cut through, then you won't get cleavage. When a mineral is fractured, the fracture "wants" to take the path where the ...


5

There are some subtleties that I'd like to add, in addition to Mark's answer. When talking about the hardness of a mineral, the nature of the chemical bonds in the crystal structure (e.g. covalent vs ionic) are not the only important thing. Crystal morphology is also important. For example, Si-O-Si and Al-O-Al bonds usually cause minerals to be hard, such ...


4

The color of a mineral can be caused by a variety of mechanisms. This is also true of amethyst, which is a variety of quartz ($\ce{SiO2}$), and can be found in many colors. The major factors responsible for the production of color in minerals fall into five categories: The presence of an element essential to the mineral composition The presence of a minor ...


4

The crystals are quartz. You can sell them but the value is dependent upon several factors: How large are the pieces? I can't tell from the photo Size and condition of the crystals affect price. Where are the crystals from? This is often the biggest factor into value. Can you Verify the location for the specimens? If the quartz crystals from somewhere ...


4

They are not synonymous. Cleavage means breaking along planes defined by crystallographic directions. For example, cubic crystals like halite, NaCl, often cleave along directions that follow the cubic form. However, with a different bond strength, like fluorite $\ce{CaF2}$, the crystals cleave most easily along octahedral directions, similar to two ...


3

Q1: A volcano consists of many lava flows that occur over a long period of time. In general, only very few of these lava flows have the right composition and the right cooling history that are required to form obsidian. This is why only parts of a volcano consist of obsidian, and by volume it's a generally a very small amount. Q2: And yes there is ...


3

I'd say it was a weathered clast of quartz vein possibly with staining and/or some fragments of the vein host rock. The crystal structure to me rules out this being chert or sedimentary quartz in origin. The weathered state doesn't though automatically mean it is re-worked from a conglomerate.


3

Bluish purple stone: Best case: Charoite (Google image it) Most likely: agate Pinkish Purple: Might be sugilite Most likely purple agate looks natural Pale blue: Blue lace agate Green: Adventurine: quartz with mica Brown-translucent (2): smoky quartz (Look carefully and see if you see silver/golden hairs... if so you have ...


3

Your question is much more complicated from mathematical point of view than it seems to be. First, I'll start with a nice photo: (source: Wikipedia). What you see is really a photo and it is almost a mono-crystal. The only problem is that we all know that it cannot be a monocrystal since it cannot tile the space. So what is it? A quasicrystal -- matter with ...


3

We have a guide on how to ask a good "Identify this rock" question (sorry it isn't easier to find. It gives you the kind of information that helps us provide better answers and helps teach you the sort of things that will help if you want to learn how to answer your own questions. From your picture, your rock appears to be made up of the mineral quartz (...


3

Not sure this is appropriate for Earth Science SE (Chemistry SE would be a better fit), but the answer is "maybe". quoting from the same Wikipedia article: Three oxides of xenon are known: xenon trioxide (XeO 3) and xenon tetroxide (XeO4), both of which are dangerously explosive and powerful oxidizing agents, and xenon dioxide (XeO2), which was ...


3

Should one assume that the mineral petitjeanite and the chemical discussed in the recent Chemical & Engineering News article Photocatalyst shreds drinking water contaminant PFOA are probably the same crystal configuration and unit cell, or can there be some variety? No you cannot assume the structure from the formula, many materials have polymorphs (...


2

I think the commenters have identified the issue. Halite does not have perfect cleavage along the {110} plane. As recorded in Mindat, Halite has perfect cleavage alone {100}, {010}, and {001}. This makes sense, as Halite is a cubic mineral (fcc), these are the planes you would expect it to cleave on.


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Double terminated crystals normally form in free floating pockets of liquid that slowly evaporated, leaving perfectly formed crystals with terminations on both sides. Unlike usual quartz formations which grow in igneous rock, double terminated crystals are more than likely found in sedimentary rock laid down by subterranean marine deposits a long time ago. ...


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Silicon carbide is covalent and can be synthesized at atmospheric pressure by the Acheson process. Temperatures may actually be somewhat higher than your range but are easily achieved by the process. 1,4 dichlorobenzene (used in moth balls) is a compound that forms crystals at low temperatures. I think the molecules in the crystal are joined only by weak ...


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In particular, in season 7 of Game of Thrones, the island of Dragonstone is revealed to contain a veritable mountain of obsidian - is such a thing possible in the real world? I would have thought that, above a certain volume, the center of the mass would be well-enough insulated so that crystallization could occur, spoiling the obsidian. Sure, an island of ...


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Yes, it has. Cody & Cody (1998), Journal of Sedimentary Research. http://archives.datapages.com/data/sepm/journals/v55-58/data/058/058002/0247.htm Abstract: Gypsum crystals were grown in experimental conditions analogous to saline terrestrial environments within bentonite clay gels by diffusion control at three different temperatures, four ...


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