The Cubes are the most captivating to me. Organic mishmash of polyhedra and assorted blobs is one thing, but perfect cubes is uniquely striking.

▲

chasil 7 hours ago | parent | next [-]

Maybe try copper sulphate?

https://crystalverse.com/best-way-to-grow-copper-sulfate-cry...

Crystal growth has been on here before. Let me see if I can find a link or two...

https://news.ycombinator.com/item?id=31105320

https://news.ycombinator.com/item?id=30487511

https://news.ycombinator.com/item?id=29779923

https://news.ycombinator.com/item?id=29255511

	▲	allan_s 6 hours ago \| parent [-]
		I did that with my kids and it was pretty cool !

▲

adrian_b 7 hours ago | parent | prev | next [-]

True, but among the minerals with cubic crystal structure it is not unusual for them to be found as crystals that are perfect regular or semiregular polyhedra, with a shape characteristic for the mineral, for instance octahedron (e.g. spinel, diamond), rhombic dodecahedron (e.g. garnet) or cube (e.g. pyrite).

I suppose that the crystals from the picture are of pyrite, which frequently looks like this.

In the antiquity, when what are now called diamonds (the Romans and the Greeks called them "Indian adamants", because they were first encountered by Europeans during the expedition in India of Alexander the Great; "adamant" meant something else in Europe) were very difficult to cut and polish, they were normally used as gems in their natural shape of regular octahedra.

Cutting diamonds from their natural octahedral shape into polyhedra with more facets, e.g. brilliant, was invented much later.

▲

namanyayg 7 hours ago | parent | prev | next [-]

Pyrite or fool's gold, lovely mathematical perfection and a great etymology to match!

▲

adrian_b 6 hours ago | parent | next [-]

Regarding etymology, for many centuries the substances that are now called "sulfides" were called "pyrites", after the "iron pyrite" i.e. the iron (II) disulfide, which is the most abundant sulfide mineral.

At the end of the 18th century, Lavoisier together with a few other French chemists have created the modern systematic chemical nomenclature, so the old term "pyrite" was replaced by "sulfide" (like also "vitriol" was replaced with "sulfate").

For who does not know, "pyrite" comes from "fire", i.e. from the pronunciation in Ancient Greek of the corresponding word that was cognate with English "fire" (Ancient Greek or Latin "p" corresponds with English "f").

Striking pyrite produces sparks, which can be used to start a fire.

	▲	thaumasiotes 4 hours ago \| parent [-]
		> Ancient Greek or Latin "p" corresponds with English "f" Similarly, ancient Greek "p" corresponds with modern Greek "f", and ancient Greek "b" corresponds with modern Greek "v". We may have done it first, but the sound change is pretty common. "B" -> "v" is arguably in process in Spanish. Something similar had already happened in Latin; compare Latin "frater" to English "brother" or Latin "fero" to Greek "phero".

▲

gus_massa 6 hours ago | parent | prev [-]

I agree. Here are a few more nice images for the GP: https://www.google.com/search?q=pyrite+cube&tbm=isch Remove "cube" from the reach, to see the not cubic samples too.

▲

dylan604 4 hours ago | parent | prev | next [-]

Especially since it's an exception that breaks the rule that straight lines are not found in nature. Not only is it a straight line, but a cube. They just look unnatural. Very cool stuff

▲

Ifkaluva 6 hours ago | parent | prev | next [-]

You can buy pyrite cubes on Etsy—I know because I also love them :)

They’re not expensive

	▲	SpaceL10n 5 hours ago \| parent [-]
		And Galena! Another wonderful metallic mineral that forms cubes.

▲

danhau 5 hours ago | parent | prev | next [-]

That pyramid shape in the amethyst is what grabbed me. Looks like something straight out of a video game. Incredible.

▲

MengerSponge 6 hours ago | parent | prev [-]

What about organic mishmashes that are shaped into cubes?

https://www.science.org/content/article/how-do-wombats-poop-...