mags
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Posts: 9
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Post by mags on Jul 24, 2012 14:17:50 GMT -5
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Post by mikeyrocks on Jul 24, 2012 15:33:53 GMT -5
what ignorance? You are seeking to expand your knowledge.... nothing ignorant about that at all.
Nice detailed photo I even like the wood backround detail in it. I am not familiar with the area or material. What I see appears to be a mass of smaller crystals in the piece; they appear to be triangular and blade like in appearance. Most crystals have a shape which will help identify them or their origin in the case of pseudomorhs. A side view or 45 degree angle shot would help a bit in this instance. The material between the small crystals appears to be rather clear silica...as in the quartz family. I would check to see if the small crystals are softer than the clear materials there. Thats what I can offer to start...lets see what others will add. Enjoy your collection and keep the great photos and good questions coming.
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Post by arappaho on Jul 24, 2012 21:19:58 GMT -5
Yes, interesting piece and good picture. Would like to hear some other opinions on it as well. Magnet Cove is a world class mineral collecting site because of the many different, and rare, minerals found there. You can Google it find tons of references. First guess would be Calcite on the large crystal. Or maybe Leucite? And what is the bed of "blade-like" crsytals? Hmmmm.....  Nice specimen. Thanks for posting. |
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Post by nichwhitt on Jul 24, 2012 21:32:29 GMT -5
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Post by mikeyrocks on Jul 25, 2012 1:15:33 GMT -5
I did some research on this one and arappaho it seems the calcite guess for the large broken crystal could be right. In my book the closest to the small blade I could find was a saddle shaped Dolomite crystal formation. From there I looked up Magnet Cove to find out where it was and more about it....quite the interesting place with around 100 minerals coming from the area. Well I looked and found several Calcite on Dolomite specimens shown and listed on the site with lots of other goodies. The link is below... This has been a good search for me.... I have gathered some nice information on this hunt. For one I did not know varicite was found in Arkansas. www.johnbetts-fineminerals.com/.../mineralmuseum/gallery2.php?... After stopping in Mt Ida and visiting the quartz mines with friends from there a few summers back; I am sure glad I am not there this time of the year. Too hot and humid to suit me in July. Better to wait for cooler weather for Arkansas and digging. |
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Post by arappaho on Jul 25, 2012 15:49:36 GMT -5
Good job, mikey, thanks! I'll go with Calcite on Dolomite as a final guess for now. The link you provided re-directs you to the sites' Home page, so I didn't get to see the specimen you are talking about, but found some other specimen pics from an area close to Magnet Cove here; www.johnbetts-fineminerals.com/jhbnyc/mineralmuseum/picshow.php?id=45828Let's see if that link works. Might be to the same stuff you were looking at. |
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mags
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Posts: 9
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Post by mags on Jul 25, 2012 15:56:03 GMT -5
Appreciate the responses. Here is pic from angle - looks a little blurry to me After looking at the links supplied by Nichwhitt and Mike, I believe it looks more like the dolomite. What is the best way to test hardness w/o causing damage to rock? Arappaho, Magnet is well known for its minerals - people from all around the world come through here gathering samples And yes Mikey, the temps/humidity here are horrible - fall weather is much more enjoyable I have many others I'll be asking help on... Attachments:
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Post by arappaho on Jul 25, 2012 16:45:22 GMT -5
A hardness, or any other test, will be hard to do satisfactorily on
a specimen like this. You may be able to find an area on the bottom that you could scratch, but it may not be conclusive.
Example; We are guessing that this is a Calcite crystal on a matrix of
Dolomite, and I'm still wondering if the matrix could be a mixture of
Dolomite and Siderite.
Calcite, hardness 3.
Dolomite, hardness 3.5-4.
Siderite, hardness 3.5-4.
A scratch test will give you a good idea, but....
The Calcite should fizz if you drop mild hydrochloric acid, or Muratic
acid, on it. The Dolomite and Siderite will, too, if they have been
pre-scratched or ground to powder.
My suggestion would be to get as close as you can with a visual ID,
and then bring your specimens to an expert on Magnet Cove
materials in your area for final verification. Sometimes, unless a
person is familiar with the material, it is still impossible to say
"for sure" what a specimen is without a chemical analysis, which
will destroy atleast part of the specimen. Someone that has seen
the material before and is familiar with it should be able to give
a pretty sure visual ID.
That expert might also be able to give you an idea on the value of
your specimens, by telling you how much he would pay to have it in
his collection.
Please don't let any of this keep you from posting more pics of your
specimens. Besides for being fun, trying to figure out what these
specimen pics are is a great way to learn. And I think we all enjoy that.
Joe
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Post by mikeyrocks on Jul 26, 2012 0:55:54 GMT -5
arappaho...yes they were some of the same specimens I had seen on the site. Not sure why the link isn't working. I had to go into the museum section, location, North America, and Arkansas to get to the page. There is 10 specimens on that page and other combos as well. I also went thru the alphabetical listing to get to dolomite (page of the 'D' listings) and oh my... what a selection of dolomite and combo's there....far too numerous to count. A nice site for photos and references... another bookmark for future reference for me.
mags I would put more effort into the visual ID of the crystals; more than attempting to check the hardness of the material. Check out the other dolomite pieces on the johnbetts site and see what you think. Pay careful attention to individual crystal shapes on your piece (use magnification to assist you) each crystal has it one or more specific shapes it will develop into.
This is also affected by the other minerals/inclusions that are present as it grows. The environment it grows in also affects growth and shape variation. Geometric shapes for crystals are similar to fingerprints and are reliable. In the case of pseudomorhs we find a material in another crystals shape and we know what crystal it replaced by the shape of the original even though the original material might no longer be present. (as accurately a description as this amateur can provide for you). As arappaho mentions do what you can and seek someone familiar with material from that locale for additional clarification. One I stumbled on in this search does collect in that area ; is Christopher Stefano, Fine Minerals who is displaying and selling specimens collected at the Jones Mills Quarry, Magnet Cove. His photos and micro-photographs are outstanding. Best of luck with your search. Look forward to seeing more of your goodies.
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mags
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Posts: 9
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Post by mags on Jul 26, 2012 13:21:50 GMT -5
Thanks for the info Joe and Mike. I book marked the John Betts site - looks like good info there. I'll look for someone locally that I can take it to - I know it's hard to positively i.d. from photo
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