What rock is this?

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Someone gave this to me a while ago, and I have no idea what it is. Here are some pictures: (sorry for my bad photography skills) http://imgur.com/gallery/ofY5p

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Type: Question • Score: 2 • Views: 801 • Replies: 14

[+3] - farmerman - 07/28/2017naaah, the crystals are tabs,quartz doesn't grow tabs,it grows hexagons

@AtomicFury,

could be a number of things with those crystals. Was your friend into rare minerals or just volume of a collection??

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Looks like quartz crystals in a slurry of sand and gravel. That's slurry not matrix.

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@emmett grogan,

naaah, the crystals are tabs,quartz doesn't grow tabs,it grows hexagons

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@farmerman,

He has tons of stuff, rare and not so rare. I might just end up bringing it to him and asking.

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@AtomicFury,

Perhaps I could help you if youd have shot them in color. Why did you choose to shoot in B&W, or did you turn the color waaay down.
One of the prisms actually looks like tourmaline but I cant tell in B&W (nd tourmalines don't usually associate with tab crystals unless its a zoisite

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@farmerman,

What are you talking about? I didn't shoot the picture in black and white, that's just the color of the rock.

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@AtomicFury,

shoot the rock on a red or green background and put in a coin for scale. Then mess with the programmed values on your cell phone. (Like enhanced, or retro)

I like to compare a minerals color against a known one from a cloth or something. Its kinda weird shooting it on what looks like a kitchen cabinet soap dish

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@farmerman,

Here is some more pictures: http://imgur.com/a/MEtxz again sorry for my **** photography, also that was the largest green thing I had, so sorry that it doesn't fill up the whole screen.

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@AtomicFury,

Pretty nice photo now, to me. I'm no help on what the rock is, but I enjoy all the rock discussions.

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@AtomicFury,

It actually looks like sphalerite (the black Xlx) in a matrix of some mineral that could be a hundred different ones. The simplest would be calcite or selenite

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@farmerman,

After doing a quick google search for sphalerite I found this: http://geology.com/minerals/sphalerite.shtml (scroll down to the fourth image) which looks very similar to the specimen I have.

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@AtomicFury,

it has many separate forms (these forms are called "habits" ). From gems to dirt red slabs. Its always associqtd with zinc deposits and sulfides The way to tell is to try to strike a small chunk against a fine toothed file and see if it sparks. Otherways involve some chemical tests that are really not worth the time cause its a fairly common but often showy mineral.I hate to wreck specimens while assaying them.

What rock is this?

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