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Rock or Mineral of the Day Thread

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I am pretty sure these rocks are Andasite - i showed it to the local mining department and they had a very similar rock in their display case described as "Andasita Textura Ocaitica" but they couldn't tell me much more. I fogot to include a penny to give some scale but the rocks in the photo are about about 2 inches x 1 inch. I was prospecting in an area in the north of Chile and the area was full of these rocks - i only spent a few hours there but didn't find any gold. I crushed up some specimens and panned them but no gold. The small ones like the one attached do not affect my detector but the large rocks, and by large I mean like about 3 feet by 3 feet are hot in that give off a real strong signal like they are full of copper or iron or some sort of metal. Does anyone have much experience with these rocks - what are they likely to consist of quartz?iron?copper? - is andasite associated with gold?

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Hi Haderly -

That's what I would call Dendritic agate but there's probably other names for it also. Nice looking cabochon. Is cutting that type of rough messy? You also make some nice jewelry. :thumbsupanim

Steve

Steve – You are close but the crystal structure is native silver. It is a pain to photograph since the shinny silver looks black in the pictures except near the edge. The matrix is calcite and it came from the Silver Islet Mine in Thunder Bay, Ontario Canada.

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Haderly-

You had me completely fooled. :grr01: Have never seen native silver in that form before. :hmmmmm: Very attractive looking material though. Must be expensive. Did you buy that rough at Tucson or from a website?

Steve

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Steve – That was my one and only eBay purchase. I never buy from eBay for many reasons but use it to research current prices. I stumbled across it and the picture was horrible but I have seen the material before. I took a chance and won the bid at $15.05. It was 240 grams so I know I got a screaming deal.

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Haderly-

That's one hell of a deal. :thumbsupanim And for 8 ounces of that rough. :thumbsupanim Wish I could find some deals like that on eBay. :rolleyes: On anything.. :twocents: I bet you're hoping he puts more up for bid.

Steve

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Here are some pic's of "sum-thin" I picked up this weekend. Looks like "pieces and parts".

Any idea's ?

Patrick.....

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I'd say you found a piece of iron stained macro crystalline quartz. Some people have referred to that as sugar quartz.

Steve

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Thanks Steve. I neglected to use something for perspective. The rock is 3 1/2" x 2". Can you tell me the "pieces and part's"? Also, would it look nice if cut and polished?

As you can tell, total NON rock guy here.....

Patrick.....

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Here are some specimens I found in Yuma this weekend...

Clear, to opaque, to white crystals that will scratch with a thumbnail. Haven't cleaned or anything and much of the matrix is still attached. I know an easy one for many, but some may not have seen it before.

IMG_20110417_075949.jpg

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Bill,

I have some gypsum crystals that look a lot like those.

Skip

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Thanks Steve. I neglected to use something for perspective. The rock is 3 1/2" x 2". Can you tell me the "pieces and part's"? Also, would it look nice if cut and polished?

As you can tell, total NON rock guy here.....

Patrick.....

HI Patrick-

Really not much to tell you. it's composed of quartz,iron stain quartz. As far as cutting it, I think you can find something a lot more suitable as far as aesthetics go. :twocents: Arizona is great state for rockhounds and a lot nice lapidary material is being found in it. No doubt you can locate something better.

Steve

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Here are some pic's of "sum-thin" I picked up this weekend. Looks like "pieces and parts".

Any idea's ?

Patrick.....

Definately leaverites Patrick !

Adam

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Bill those really look like selenite crystals ...I think Selenite is a variety of Gypsum They are cool, especially the HUGE ones..

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Darn Adam. I thought I had the find of the Century.

Patrick.....

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Bill those really look like selenite crystals ...I think Selenite is a variety of Gypsum They are cool, especially the HUGE ones..

Thanks Adam! I knew it was some form of Gypsum but I will go back to the books. Isn't Selenite the mineral that also forms the "rose" type clusters?

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Im Pretty sure it would be considered selenite...Gypsum would be correct too as was already mentioned. Yes, in some areas they form into Selenite "roses"... I think there is a spot for those down by St. David? or something...

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Im Pretty sure it would be considered selenite...Gypsum would be correct too as was already mentioned. Yes, in some areas they form into Selenite "roses"... I think there is a spot for those down by St. David? or something...

Cheers Johnno

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I have been following this thread and have seen several good looking specimens, decided to post a photo of a rock I ran across in the Mother Lode.

I don't have the knowledge of most of the people posting here so I can't elaborate.

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Will it scratch with a finger nail or knife? It looks like a type of serpentine we find in southern Oregon But it could also be in the jadeite/nephrite family. Hardness test will help narrow down the possibilities.

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Will it scratch with a finger nail or knife? It looks like a type of serpentine we find in southern Oregon But it could also be in the jadeite/nephrite family. Hardness test will help narrow down the possibilities.

I didn't get any scratch marks with finger nail. Easily scratches with a Henckels kitchen knife with a sharp tip.

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I'm pretty sure it's from the serpentine group also. Just not sure of the variety. But an interesting find.

Steve

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Being that soft I would say serpentine. Serpentine usually has slick almost greasy feel to it similar to the feel of soapstone. Check if it is magnetic. I have serpentine with hematite, with chromite and with pyrite. I would guess that your piece probably has hematite but it could be chromite or even something completely different.

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Very similar to this specimen....

IMG_20110429_064314.jpg

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