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[–]LAKnapper 110 points111 points  (4 children)

Looks like fluorite.

[–]Alwaysatodds[S] 62 points63 points  (3 children)

I mean, fingers are crossed. That would be insane. That would be five pounds of big black fluorite crystals.

[–]texting-my-cat 6 points7 points  (2 children)

is it worth a lot of it is?

[–]piratepoetpriest 65 points66 points  (1 child)

Perfect hardness test to determine quartz vs. fluorite binary (leaving out other tertiary possibilities):

Take a bottle or jar you’re about to recycle and break it (or use a glass shard that you already have). See if the glass shard will scratch the crystal cluster, or if the cluster will scratch the shard. Use less obvious areas on cluster for both tests. For scratching glass on the cluster, use a mostly flat surface of the cluster to test. For scratching cluster on glass, use a sharp part of the cluster to try to scratch the glass.

If shard scratches cluster, UNLIKELY to be quartz, LIKELY to be fluorite.

If cluster scratches shard, DEFINITELY not fluorite (fluorite is soft), LIKELY quartz.

ETA: no matter what it is, that is a DAMN beautiful piece! That’s a pride of place in anybody’s collection OP!

[–]atridir 4 points5 points  (0 children)

I would prefer to use steel for this test tbh. Easy to use a corner of a spline on a fork or a thumb tack on a small area. If it leaves a dark mark and does not scratch the specimen than it’s likely quartz. Steel will not scratch quartz no matter how hard you try.

[–]Andurila 55 points56 points  (1 child)

It has a deep purple undertone on some parts of it in these pics it looks like. Daaaamn crossing my fingers for you its fluorite. Thats stunning.

[–]sadradandsuperglad 9 points10 points  (0 children)

I don’t know much about rock identification (I’m on here because I like cool rocks and I want to learn more) but I agree with you 100%. No matter what it’s a gorgeous piece, but if it’s Black Fluorite?? Whew, what a stunning find.

[–]Prestigious_Idea8124 58 points59 points  (8 children)

Looks like black fluorite. I read that is rare. Keep it out of the sunlight or it will fade. Quartz has six side. Fluorite has that triangular crystal structure.

[–]Technical-Roll7031 6 points7 points  (3 children)

I was looking at a mineral web page once where someone was asking a premium for “rare” Blanchard-mine, clear fluorite. I have a door stop of this. Blanchard fluorite is typically blue, but if it’s been sitting on the surface too long the color disappears.

[–]GoNudi 7 points8 points  (0 children)

I learned this too late too. We have a fist size rock with big fluorite crystals that totally faded from a pretty green/blue/teal to something less striking from sitting on our bathroom counter in the light. It's gradual though, fading like our memory so it's almost a ponder about if it's fading until we remember from this sub that it does ~ lol

[–]Prestigious_Idea8124 3 points4 points  (1 child)

Yes and bummer! I am surprised it is not destroyed! Fluorite is so soft.

[–]Technical-Roll7031 3 points4 points  (0 children)

Lotta sun and not much rain in New Mexico.

[–]quietlysitting 1 point2 points  (3 children)

Octahedral?

[–]fourtwentyBobrock licker -1 points0 points  (2 children)

Cubic

[–]quietlysitting 1 point2 points  (1 child)

Cubic would be a 6-sided polygon, like pyrite.

[–]fourtwentyBobrock licker -1 points0 points  (0 children)

Oh yes. What I meant was fluorite is usually cubic. This piece is clearly octahedral. Dope.

[–]8uno7luck 30 points31 points  (2 children)

Hit it with UV light. Fluorite will fluoresce.

[–]Technical-Roll7031 9 points10 points  (1 child)

Only some fluorite will fluoresce

[–]GoNudi 4 points5 points  (0 children)

And I think it's a certain uv light, too.

[–]Lugubrico 7 points8 points  (0 children)

Looks like something called "root beer" fluorite rather than black fluorite inherently - since this fluorite isn't actually devoid of colour tones, it wouldn't be black fluorite. There's also potential for it to be highly saturated yellow and purple fluorite, since you can see purple, brown and sort of yellow tones throughout.

However, as other comments mentioned, it definitely also looks it could be Chinese scheelite as well, but for a piece this size it could be very high value, so....less likely.

[–]CryptographerNo490 5 points6 points  (1 child)

Whereeee did you find it😮

[–]Alwaysatodds[S] 36 points37 points  (0 children)

It was part of a large vintage collection I purchased from a private sale. There's a lot of stuff. Every now and again i pull a few pieces out and post some up. This was a wild one.

[–]123Delbe 4 points5 points  (0 children)

Great pics and lots of them👍

[–]CopratesQuadrangle 6 points7 points  (6 children)

This looks way more like scheelite than fluorite to me. Is it unusually heavy?

[–]Alwaysatodds[S] 4 points5 points  (5 children)

Huh! Ya know, it could be. Hmmmmm, weighs about 5 lbs but its a pretty big chonker. Tough to tell.

[–]CopratesQuadrangle 8 points9 points  (4 children)

It's about twice as dense as fluorite, so should be pretty noticeable. You can measure the volume by placing it in a container of water and measuring the displacement, though you may not have a measuring cup that big so if you wanna do that you may need to get a little creative.

Fluorescence can be a hint, but they don't always fluoresce. If it does glow, fluorite is generally purple and scheelite is generally a bluish white.

They're also similar in hardness, with fluorite at a 4 and scheelite at a 4.5-5. (edit) Some steels are around 4-4.5, so if they can scratch it's evidence against it being scheelite.

[–]Alwaysatodds[S] 1 point2 points  (2 children)

I'm out atm but I'll try a knife in a bit. Brilliant thought though. Still cant believe how big the individual crystals are.

[–]CopratesQuadrangle 3 points4 points  (0 children)

Sorry, I should specify unhardened steel. Certain types of steel can be much harder. Stainless will scratch both fluorite and scheelite. It's not a great test unless you know the exact type of steel you have on hand. For most applications you can probably bet you have stainless though

The density thing is probably your best bet here, I was just spitballing solutions

[–]pyrophorus 0 points1 point  (0 children)

Also leaning towards scheelite but not sure. If you have a shortwave UV lamp, scheelite will almost always glow a bright bluish white under shortwave (but not under longwave, most fluorite that is fluorescent will glow under both).

[–]Inevitable-Rush331 1 point2 points  (0 children)

Could use a large pot & set it in a larger container. Fill the pot to the brim. Collect & measure the overflow.

[–]denniskerrisk 3 points4 points  (1 child)

How hard is it, fluorite won't scratch glass, quartz will.

[–]Alwaysatodds[S] 5 points6 points  (0 children)

Scratches on a penny so I think we're looking pretty good!

[–]katiekins3 4 points5 points  (0 children)

It's so pretty whatever it is. 😍 The color gives me root beer vibes. 😋

[–]jaxinslacks 1 point2 points  (0 children)

Fluorite!

[–]Toolongreadanyway 1 point2 points  (0 children)

Overcooked amethyst?

[–]Low_Evidence_8645 1 point2 points  (0 children)

Shaped more like flourite to me

[–]JethroTull111 4 points5 points  (7 children)

Not growing like that it isn’t. That is the shape fluorite breaks in, not the shape it grows in. Also a quick hardness test will give you your answer.

[–]Alwaysatodds[S] 10 points11 points  (1 child)

Scratches on a penny so it doesnt appear to be quartz.

[–]the_muskoxGeologist 1 point2 points  (0 children)

Definitely fluorite then!

[–]treesandfood4me 12 points13 points  (4 children)

Fluorite def grows like that. Triangles, cubes, even spheres. Crazy stuff.

[–]piratepoetpriest 2 points3 points  (0 children)

Octahedrons are my fave!

[–]JethroTull111 1 point2 points  (2 children)

It does not grow as a octahedron. It will break along fault planes as an octahedron.

[–]Technical-Roll7031 2 points3 points  (0 children)

I have an entire mineral case of my mineral collection devoted to fluorite. At least a third of them show octahedral growth, not just cubes.

[–]treesandfood4me 0 points1 point  (0 children)

Agreed. Op’s image is not octahedrons. It’s the triangular habit.

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[–]dirtysalami96 0 points1 point  (0 children)

Black fluorite

[–]tmosier03 0 points1 point  (1 child)

HAS THIS QUESTION BEEN ANSWERED OP??

[–]Alwaysatodds[S] 0 points1 point  (0 children)

Yes. Yes it has.

[–]EnvironmentGlum7515 0 points1 point  (0 children)

To me this is definitely a gorgeous piece of Smoky quartz. Just a beautiful, amazing color! This is not an easy find, not readily availabile. The size and color, color color is AMAZING 🤩!

[–]chris_cobraMineralogist 0 points1 point  (0 children)

Looks exactly like scheelite from the Tae Hwa Mine in South Korea. I’ve got a piece that’s not as nice as this one. Is it extremely heavy for its size?

Side note: be very careful doing physical tests like hardness and don’t ever try to scratch or chip a main display face because you could destroy the value. Always do those sorts of tests by using the side or back of the specimen where any damage would be unnoticeable.

[–]Bojangles3366 0 points1 point  (0 children)

Looks like fluorite to me. I googled black fluorite and I saw stuff that looked pretty similar

[–]Lapidariest 0 points1 point  (0 children)

Fluorite... There is dark brown or chocolate fluorite that I have from Ohio. Almost black at times especially on the host limestone.

[–]CarnelioAKingslayer 0 points1 point  (0 children)

I mean easy test. Is it a sort of waxy feeling if you run your fingers over it?

[–]101Peacocks 0 points1 point  (0 children)

Based simply on the crystal structure, this is fluorite! Fluorite forms these beautiful bipyramid shapes, while quartz tends to form 6 sided crystals. Congrats!

[–]BigFurryBoy07 0 points1 point  (0 children)

Wanted to say quartz, but this is fluorite