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Identity HelpNot something I have seen previously

23rd Aug 2017 03:59 UTCnewcollect

Hi. I am fairly new to collecting and have come across a large specimen that I can't seem to figure out what it is. It looks like calcite with crystals on the reverse however the front is very interesting and I was hoping someone might be able to tell me what it might be. It is very large (see ruler on pictures) and it has broken in two places and had been glued back together (was that way when I received it).

Thanks for any help!

newcollect

23rd Aug 2017 06:00 UTCKevin Conroy Manager

Is this specimen slightly concave, with the last photo being the inner part? If so this may be a post-mining deposit.

23rd Aug 2017 06:52 UTCnewcollect

No, it's not concave on the reverse side. I have attached some additional photos. First 2 are of the front with all the gypsum? crystals and the last one is a bigger overview of the reverse where the larger calcite? crystals are imbedded in the silverish grey host rock.

23rd Aug 2017 11:50 UTCReiner Mielke Expert

The overall appearance does not look natural. Where did you find it?

23rd Aug 2017 18:39 UTCnewcollect

Oh it's natural. Zoom in on any of the photos and look at the mineral structure. I didn't find it, I paid a very small amount for it because it was so unusual.

23rd Aug 2017 18:54 UTCUwe Kolitsch Manager

So which locality does the label say ...?

23rd Aug 2017 19:18 UTCBob Harman

I agree with the others, having serious doubts that that is natural. Unless, as UWE says, you can come up with a legitimate label of where it originally was found, I think it is man created. Stating that you bought it rather than found it doesn't tell me anything.

Having to hazard a guess, I might think it is a part of demolished road/bridge type infrastructure or an old demolished house or commercial building and been decomposing (and maybe (recrystallizing) in a landfill for the past 50+ years. CHEERS.....BOB

24th Aug 2017 00:40 UTCWayne Corwin

What's it glued with?

lets see the cross sections

24th Aug 2017 01:48 UTCStephen Turner

I think you have a couple of possibilities here. It looks like you have a bladed carbonate (or baryte if it is real heavy) with some sulphides (?maybe sphalerite and pyrite or marcasite in your second photo). This can occur in epithermal veins and your piece could have been peeled or hacked from a vein wall like some deposits I have seen in Peru.

It also looks like the bladed carbonate + sulphides which result from flash boiling in geothermal plants and coats (and occasionally blocks) the back pressure plates. Such material is hard to get and can contain spectacular gold and silver values, as at Wairakei in New Zealand. If your specimen is curved in profile, like Kevin suggested, then this could be a possibility.

Either way I think you have some nice material and a good example of bladed textures, which geologists working in epithermal Au-Ag deposits commonly call 'boiling textures'.

24th Aug 2017 03:06 UTCMatt Neuzil Expert

It is hard to know what it is when there is no information on the piece. Sometimes a rock or mineral is so recognizable that it is almost unmistakable. In the mineral community, without documentation it's always going to be an unknown.

You mention you acquired the piece. Who gave it to you or sold it? They had no information for it? They gave no verbal insight as to what it was?

To me it looks odd. The backside looks sandy. It is odd looking and nothing like anything I have seen. Something resembling quartz seems fragmented and angular not euhedral. I don't have any offering as what this could be outside of something man-made as if this was in some sort of tank or container and crystallized as the solution evaporated.

To me it seems poorly repaired. The glue reminds me of dried school glue. With such a large piece I suppose you would need to be skilled in repair? I think to possibly get a definitive answer about your mystery piece you'd have to break off some of the crystal and run tests on the piece.

24th Aug 2017 03:25 UTCDana Slaughter 🌟 Expert

It's an albite (var. cleavelandite) with muscovite from Minas Gerais, Brazil.

24th Aug 2017 06:05 UTCStephen Turner

You're right Dana - I should have zoomed in further. What I thought was sulphide is definitely mica. And I have a smaller one of those too!

24th Aug 2017 08:11 UTCIan Nicastro

Nice catch Dana.

24th Aug 2017 19:50 UTCnewcollect

thank you for all the comments and help.

24th Aug 2017 21:24 UTCnewcollect

is there any value to this mineral? I know if it is broken there may not be very much value (that is why I didn't pay a lot for it).

24th Aug 2017 21:54 UTCBob Harman

I may have been wrong with my Identification, but without a definitive label and those poorly repaired breaks, I don't see it having much value at all. In fact you might have to convince other collectors that it is indeed natural. CHEERS.....BOB

24th Aug 2017 23:24 UTCIan Nicastro

Around $15. What people really look for with this sort of stuff are matrix pieces with aesthetic minerals coming off the matrix (such as beryl, tourmaline, quartz, etc...) and then the matrix being coated with the bladed albite like this, to give a nice contrast... something like this: https://www.mindat.org/photo-535832.html But just a matrix of albite blades isn't that valuable unless the blades are nice and pristine and large, these are small blades and have damage.

25th Aug 2017 04:32 UTCDana Slaughter 🌟 Expert

I think that the specimen value and appeal might be increased by removing the glue and returning the specimen to three pieces. You could keep the portion you deem best and trade or sell the others for perhaps $10 each. The albite seems damaged and there are no large and dramatic muscovite/lepidolite blooms attractively dotting the specimen to add interest and value...and the overall shape and poor repair greatly reduce its value and desirability. Join a rock and mineral club and donate the other two to the club---would be a great way to introduce yourself to the community. The lack of label doesn't detract as it is almost certainly from Minas Gerais, Brazil but there are several occurrences for the mineral in MG and I wouldn't be comfortable attributing a more specific locality to the piece. These specimens are quite common and collectors typically seek those associated with sharp quartz crystals and/or Tourmaline Group minerals.

Thanks for posting, welcome to the hobby and to mindat.org and follow your own interests and likes! Personally, I love Feldspar Group minerals and feel that they are woefully under-appreciated and under-valued in good specimens.

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