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Post by Jugglerguy on Apr 18, 2017 16:08:05 GMT -5
Last summer I found some green quartz here in northern Michigan. It's the second time I've found this rock. The other time was before I started tumbling. I tumbled some of the first rock and it was very fractured. When I found this rock, it was a large broken rock and I didn't bring all of it home because the first was so fractured. I just cut some over the weekend, and was pleasantly surprised at how solid it was. I might have to go look for the rest of it. I think it's quartz. I did some reading on aventurine which was described as having a "shimmering or glistening effect termed aventurescence". I don't think my rock has that, but it looks an awful lot like the pictures from a Google search. So what do you think, aventurine, green quartz, or something else? This end cut and slab are six or seven inches long.   Close up:  Picture of aventurine from Wikipedia:  |
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Fossilman
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Post by Fossilman on Apr 18, 2017 16:23:01 GMT -5
Looks like green quartz.......It tumbles great though!!
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Don
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Post by Don on Apr 18, 2017 16:56:15 GMT -5
adventurine is green quartz.
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Post by Jugglerguy on Apr 18, 2017 19:15:31 GMT -5
adventurine is green quartz. But is all green quartz aventurine? |
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Post by Peruano on Apr 18, 2017 21:01:53 GMT -5
How would I tell it from green quartzite? It looks rather sugary to me. Quartzite can run the spectrum from grainy to relatively smooth.
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rastageezer
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Post by rastageezer on Apr 19, 2017 3:33:49 GMT -5
Looks exactly like a hunk of green quartz I have.
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Sabre52
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Post by Sabre52 on Apr 19, 2017 6:17:30 GMT -5
I may be mistaken, but I seem to remember that the difference between aventurine and "just plain quartzite" is the presence of tiny mica flakes in the aventurine. The mica is often in bands and lends a bit of flash or sparkle to the aventurine. Sometimes the softer mica even undercuts a bit making it a bit more difficult to get that mirror finish on some aventurine. To me your specimen does look like green quartz/quartzite. Have a big block of it in the garden....Mel
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metalsmith
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Post by metalsmith on Apr 19, 2017 11:12:50 GMT -5
aventurine has aventurescence; aventurine with no aventurescence = green quartz link |
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Deleted
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Post by Deleted on Apr 19, 2017 11:16:54 GMT -5
Rob, Mel nailed it.
Do you see little mica sparkles? Aventurine.
No? Quartzite.
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Sabre52
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Post by Sabre52 on Apr 19, 2017 13:27:41 GMT -5
Wow aventurescence. Cool word! Sounds like what happens when Blue spooks a turkey off her nest, a big ole aventurescence. Hell, he aventuresces all over the dang place in four directions at once *L*....Mel
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Fossilman
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Post by Fossilman on Apr 19, 2017 16:42:13 GMT -5
I find a lot of this green quart in the Yellowstone River,- Montana...
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Post by Jugglerguy on Apr 19, 2017 17:52:00 GMT -5
I don't see any mica sparkles, so it must not be aventurine. Thanks everyone.
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Post by johnjsgems on Apr 21, 2017 13:20:29 GMT -5
I think aventurine was used pretty commonly as a name for green quartz before the Chinese started cooking up chalcedony in many different colors. Now there is "aventurine" in every color. A rock by any name is still a rock.
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Post by Bluesky78987 on Apr 22, 2017 9:22:08 GMT -5
Wow aventurescence. Cool word! Sounds like what happens when Blue spooks a turkey off her nest, a big ole aventurescence. Hell, he aventuresces all over the dang place in four directions at once *L*....Mel ROTFLMAO Mel! I'm gonna need a video of that . . . I'm cracking myself up with the mental image. |
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jahzilla1
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Post by jahzilla1 on Jul 16, 2020 22:03:07 GMT -5
Ok not green quartz, not at all. As far as I can see which isn't far for a person uneducated in the geology world. All natural green quartz comes from one place and that's Brazil, any other green quartz is made that way by irradiating amethyst. My thoughts on this was maybe it was a serpentonite, like lizardite, which is found in Michigan,
Or a chalcedony, like Chrysoprase as there are nickle mines in Michigan, which would produce chrysoprase, other then that I am stumped
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jahzilla1
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Post by jahzilla1 on Jul 16, 2020 22:08:41 GMT -5
adventurine is green quartz. But is all green quartz aventurine? Actually no, adventuressence is whatakes it different then green quartz, as green quartz does not have it |
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jahzilla1
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Post by jahzilla1 on Jul 16, 2020 22:33:14 GMT -5
I think aventurine was used pretty commonly as a name for green quartz before the Chinese started cooking up chalcedony in many different colors. Now there is "aventurine" in every color. A rock by any name is still a rock. Except quartz is not a rock, it's a mineral. Minerals are what rocks are made of. |
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Post by catmandewe on Jul 16, 2020 22:37:48 GMT -5
Prasiolite
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Post by rmf on Jul 17, 2020 14:04:04 GMT -5
Aventurine is green quartzite. Sometimes with pyrite and usually with flakes of mica. It is metamorphosed sandstone typically of a fine grain. Yours is aventurine based on the fracture. At least from this distance.
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gemfeller
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Post by gemfeller on Jul 17, 2020 17:39:49 GMT -5
RE: "aventurine," "aventurescence." This may seem nerdy but I laugh to myself every time I see the stone's name spelled "adventurine." It may be an adventure to collect and cut but the word has no "d." Putting on my gemology hat:
Aventurescence's name is derived from the Italian word "aventura," meaning "by chance." It was applied to Italian-made goldstone (glass with copper filings) which mimics the appearance of some types of sunstone, especially that from India.
Natural stones displaying aventurescence include aventurine quartz, rutiliated quartz and sunstone feldspar. Those three fall into the category of "Mirror stones" that reflect bright light back to the eye in a disorganized way. When those mirror reflections are organized into stars or cat's-eyes they become a separate category of so-called "phenomenal gems:" gems that display optical phenomena like fire agate, opal, labradorite, moonstone etc.
In gemology each optical phenomenon has a specialized name: "asterism" for stars, "chatoyance" for cat's-eye type gems, "adularescence" for moonstone, "laradorescence" for labradorite and so on. There's a great little down-to-earth book titled "Phenomenal Gems" by Fred and Charlotte Ward that helps a lot in understanding those terms and why they're applied.
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