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Posts posted by jcervay

  1. 2 minutes ago, Morlock said:

    You're right Dan. I think what he has is malachite and calcite. Malachite is copper.carbonate.

    It's definitely malachite. The crystal itself was confusing me. I tried scratching it with all that stuff and nothing was working for me. I stopped fussing with it and broke a small crystal off. I'm pretty sure now that it's calcite. 

    • Like 1
  2. Picked this up at a small rock shop in Ohio. No labels, no idea where it's from. My original thought was calcite on quartz without looking closely. Emailed seller, they say aragonite.  There is a strong reaction to vinegar. But when I tried to scratch the crystals themselves, I can't discern any visual or tactile evidence of scratches from steel, quartz, or from an aqua. The hardness surprised me. The smaller crystals on the matriz must be calcite . Any thoughts? 







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  3. 31 minutes ago, adam said:


    May I make a few comments? 

    Do you have a copy of the National Audubon Society`s field guide to North American Rocks and minerals? 


    Im pretty serious and I do have reference material. Books, mindat, the entire internet really...all readily available. However, to ask the particular question about if and how acid could affect a certain mineral, seemed like other people, like yourself, would be the better resource. 

    I do apologise for not including the location, I forget that other people don't know that I only have time to collect locally in PA. This came from PA. Previous posts have mentioned when I have something of unknown origin, things I have bought at auction. I don't like to influence other's opinions, I've seen too many people jump on ID bandwagons in other formus. But I agree that my posts can be too vague. Forgive me?

    I will check to see if there is a location specific handbook, great idea

    • Like 2
  4. After soaking a few pieces of quartz in muriatic acid, what I thought could be small radials of pyrite, are now green. Any ideas? Did the acid affect the mineral, or did it simply remove an iron oxide crust. Pics are really hard to take, it's so small. Including a before pic too. Third pic shows the color the best.








    • Like 1
  5. 7 hours ago, LowPoint said:

    Mine's not as pretty as yours,....  I call it "Tyrannosaurus Geode"

    Definitely really cool though. Perfect name! I can't say that this is the only one I've saved though. Lol. I recently brought home a piece that was at least 10 pounds with a few points on it, but aesthetically beautiful.(to me haha!)

  6. 19 minutes ago, BMc said:

     I find them interesting, and enjoy looking at the different shapes, sizes and colors of various crystals.   

    Completely agree, there's a charm, to me, in seeing the various formations and intricacies

  7. 20 hours ago, 4meter said:

    Very nice specimen!  Might be the mineral Marcasite which looks has the same chemical make-up as Pyrite, but Marcasite unstable and crumbles into a powder with time.

    Good though on the marcasite. There is actually a little cube formation here and there. Hard to see here

  8. I'm sure you guys have seen this before, but I picked this up yesterday cause I thought it was cool how the black had grown in between and around the crystals. Broke it accidentally when I split the rock, but now I can really see the shape it took around the quartz.









  9. 6 hours ago, 4meter said:

    Place a drop of weak acid on a sample of the brown mineral.  Calcite will fizz, Siderite will not fizz with the addition of a weak acid.

    No strong reaction to the vinegar. Not that I would expect from calcite

  10. 8 minutes ago, adam said:

    Siderite?, Is that something to do with iron?  First thing I thought was calcite or maybe barite.

    Iron Carbonite. Not heavy enough for barite i don't think. No noticable reaction to vinegar that I would expect from calcite. 

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