worthy 55 Posted November 3, 2011 Share Posted November 3, 2011 This one is for you rock hounds out there. I picked this up in a thrift store for half a buck and would like to know what kind of crystals these are? I know nothing about these,more pic to follow thanks. It's my bone!!! Link to comment Share on other sites More sharing options...
worthy 55 Posted November 3, 2011 Author Share Posted November 3, 2011 more pic. It's my bone!!! Link to comment Share on other sites More sharing options...
worthy 55 Posted November 3, 2011 Author Share Posted November 3, 2011 last one. It's my bone!!! Link to comment Share on other sites More sharing options...
Scylla Posted November 3, 2011 Share Posted November 3, 2011 Selenite I think, could be calcite too Link to comment Share on other sites More sharing options...
Lloyd Posted November 3, 2011 Share Posted November 3, 2011 I have quite a few geodes with Calcite in them, and none of them look anything like that, Calcite tends to be somewhat square in shape and I also have never seen anything like those dark centers in any Calcite... so I'd rule out Calcite. I don't have any geodes with Selenite in them but none of the Selenite I do have has those dark centers either, although the crystal itself looks like it could be Selenite. So, bottom line, I have no idea but I sure do like the look of that geode. Link to comment Share on other sites More sharing options...
Wrangellian Posted November 4, 2011 Share Posted November 4, 2011 Good deal! I think calcite, and the dark centers are what the crystals grew on.. but not 100% sure. I do know calcite comes in many forms, so it's hard eliminate that possibility by the shape. Link to comment Share on other sites More sharing options...
surfergirlatx Posted November 4, 2011 Share Posted November 4, 2011 That is really, really nice!!! "The road to success is always under construction." Author Unknown. Link to comment Share on other sites More sharing options...
Lloyd Posted November 4, 2011 Share Posted November 4, 2011 (edited) Ok, this is going to be pretty far out but... looking closer at the back and seeing that, in at least one place, you can see the same shape as the circular crystals inside, I'm wondering of this could possible be mineralized crinoid stems. To me, that would explain the dark centers. I have one or two geodes from KY that are formed from a crinoid Calyx but I have none that contain anything that remotely resembles stems... At any rate, like I said, I think this theory is pretty out there but since I had the thought I'd figured I'd put it out there for opinions. Edited November 4, 2011 by Lloyd Link to comment Share on other sites More sharing options...
tracer Posted November 4, 2011 Share Posted November 4, 2011 the problem with the piece is that, not knowing where it came from, you more or less would have to either be able to test the mineral to find out what it is, or both recognize the crystalline structure and also know that it is unique to the particular mineral and excludes others. if you really want to know what it is, i'd try to email the pics to some people who are mineral dealers at various websites and see if you get any consensus from them. the mineral doesn't look like any calcite that i've seen, and doesn't look like any quartz i've seen. selenite is an intriguing concept but i don't know enough about it's crystalline structure and habits to venture an opinion, other than to say that i always tend to think evaporites in these kinds of situations once i've decided a mineral isn't quartz and isn't very hard. i'm thinkin you should return to the thrift store and demand they give you five bucks for causing a conundrum. Link to comment Share on other sites More sharing options...
Taxman56 Posted November 4, 2011 Share Posted November 4, 2011 good buy, i found a lot of rock bargins at yard sales and auctions Link to comment Share on other sites More sharing options...
ashcraft Posted November 4, 2011 Share Posted November 4, 2011 . i'm thinkin you should return to the thrift store and demand they give you five bucks for causing a conundrum. Maybe that should be "causing a corundum"? Brent Ashcraft ashcraft, brent allen Link to comment Share on other sites More sharing options...
Ludwigia Posted November 4, 2011 Share Posted November 4, 2011 (edited) I'd have to agree with Tracer. It's just about impossible to make out the morphology of the crystals and the larger ones with the central point look like aggregates anyway. The geode looks like it might be of volcanic origins, but you'd need to analyze it and know where it came from. Those could also be zeolite crystals, but it's really hard to tell from this vantage point. Best thing is to place it in the hands of someone who can give you an educated opinion. Edited November 5, 2011 by Ludwigia Greetings from the Lake of Constance. Roger http://www.steinkern.de/ Link to comment Share on other sites More sharing options...
worthy 55 Posted November 4, 2011 Author Share Posted November 4, 2011 Thanks everyone , there is a small rock shop in town so I'll try to take it by there this weekend and see if they may know what it is. B) It's my bone!!! Link to comment Share on other sites More sharing options...
Scylla Posted November 4, 2011 Share Posted November 4, 2011 I didn't even think of zeolites, could be OK so what is the hardness of that mineral? I think the dark centers are what the relatively clear crystals formed on, right? Does it fizz when you drop a bit of it into vinegar? Link to comment Share on other sites More sharing options...
bdevey Posted November 4, 2011 Share Posted November 4, 2011 Very nice find. A few years ago, I found a geode, that I could not figure out. The crystals were silica [quartz], but they were in a form I had never seen. The cyrstals did not look like yours' but they also had a darker core. I had someone id it as a pseudomorph. I wonder if thats what you have there? here is another link Bob Link to comment Share on other sites More sharing options...
tracer Posted November 4, 2011 Share Posted November 4, 2011 there are polymorphs of minerals that are true alternate forms of the mineral. a pseudomorph would be a replacement of a different mineral and so the result might appear to have the crystalline form of the original mineral but would likely be a crypto- or microcrystalline replacement of the shape of the original crystals, and not actually visible crystals themselves. Link to comment Share on other sites More sharing options...
BobWill Posted November 5, 2011 Share Posted November 5, 2011 Have you tried a hardness test? Link to comment Share on other sites More sharing options...
worthy 55 Posted November 5, 2011 Author Share Posted November 5, 2011 No test yet but here are a few more closeup pic. B) It's my bone!!! Link to comment Share on other sites More sharing options...
worthy 55 Posted November 5, 2011 Author Share Posted November 5, 2011 More pic's. It's my bone!!! Link to comment Share on other sites More sharing options...
worthy 55 Posted November 5, 2011 Author Share Posted November 5, 2011 Last pic. It's my bone!!! Link to comment Share on other sites More sharing options...
Wrangellian Posted November 5, 2011 Share Posted November 5, 2011 I'd put money on 'calcite', though not a lot..... I have a similar geode, with calcite among the quartz tho' not in this exact form. These are definitely volcanic in origin though, and it looks like my earlier call was correct as to the crystals forming around a nucleus (a bump in the geode wall), and the crystals are twinned or terraced - if you eliminate the 'duplication' of the twinning you might see the basic calcite angles there. Calcite has all sorts of 'habits'. Link to comment Share on other sites More sharing options...
Scylla Posted November 5, 2011 Share Posted November 5, 2011 Calcite feels more greasy than selenite. Selenite (a variety of gypsum) tends to feel less cold to the touch. (trying to think up non-destructive ways of IDing the crystals) Hey see if it splits a laser pointer beam into two! Link to comment Share on other sites More sharing options...
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