whyofquartz
spending too much on rocks
So, Africa is smaller than I expected...
Member since December 2019
Posts: 316
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Post by whyofquartz on Dec 14, 2019 10:18:35 GMT -5
I have asked this question in other circles and the most common answer I get is Mohs, streak, fracture. From what I can tell this is how Minerals are identified but rocks are amalgamations of minerals and this is not exactly what i am asking. For example: Agate, Jasper, Adventurine, and Chalcedony are all comprised of the mineral Quartz so scratching them tells me only that they are a quartz. Uncle Charles would tell me, in his thick Appalachian accent "this is leopard jasper and this is an agate, and this is Petrified grapevine from south Texas" I have seen people on here say "oh this is Pet. Palm and this is Bumble Jasper and this is bullcrapine from the south slope of the north part of the eastern Ouachitas" that is what I want to know, how do I learn the Names of rocks and what determines the Names of rocks, I mean there is bound to be Hershey brown chert and quartz outside of Medina and Frio county Texas but that stone is not Devine Chocolate Agate. Does this knowledge come from books? from experience? or is it all made up on the fly?
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pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
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Post by pizzano on Dec 14, 2019 12:37:27 GMT -5
I have asked this question in other circles and the most common answer I get is Mohs, streak, fracture. From what I can tell this is how Minerals are identified but rocks are amalgamations of minerals and this is not exactly what i am asking. For example: Agate, Jasper, Adventurine, and Chalcedony are all comprised of the mineral Quartz so scratching them tells me only that they are a quartz. Uncle Charles would tell me, in his thick Appalachian accent "this is leopard jasper and this is an agate, and this is Petrified grapevine from south Texas" I have seen people on here say "oh this is Pet. Palm and this is Bumble Jasper and this is bullcrapine from the south slope of the north part of the eastern Ouachitas" that is what I want to know, how do I learn the Names of rocks and what determines the Names of rocks, I mean there is bound to be Hershey brown chert and quartz outside of Medina and Frio county Texas but that stone is not Devine Chocolate Agate. Does this knowledge come from books? from experience? or is it all made up on the fly? Most of us who are members here would consider ourselves amateur geologist........it is a science and there are (as you have discovered) specific classifications, categories, grades, chemical elements, ect., that play a part in identifying rocks..........not all "rocks" are minerals or contain mineral trace elements. Over the centuries rock collecting hobby folks have found it easier to "name" a specimen based on the places they found them or the person's name who first identified the specimen, and simply labeled them agates, jasper, ect...........it's reallly a much more complicated process than that and yes, the information your'e seeking most certainly comes from books, lots of them.......!
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Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Dec 14, 2019 13:03:08 GMT -5
that is what I want to know, how do I learn the Names of rocks and what determines the Names of rocks, I mean there is bound to be Hershey brown chert and quartz outside of Medina and Frio county Texas but that stone is not Devine Chocolate Agate. Does this knowledge come from books? from experience? or is it all made up on the fly? The best determinations are a chain of provenance from the miner to yourself. For unknown pieces, there are ways to nail down an origin even more concretely, but they require gemological equipment that few of us can access (e.g., Ramen scanners) and/or which cost far more to have a lab test than the value of the material in question. Short of that, then experience is probably the best guide. Pattern, color, density, translucency are all factors. That said, there can often be a great deal of diversity within a deposit, so you are dealing with a range of those factors. Not every piece, even from the same chunk of material, fits neatly with the paradigmatic model of what a piece of x from y is supposed to look like. Identifying from a photo is especially fraught, as you mainly have pattern on which to go (colors in a photo can vary from in-hand). Sounds worse than it can be. For many materials, pattern and color from a particular deposit are unique enough to get an ID with reasonable accuracy if they are anywhere close to the prototypical material from that locale. For other materials, such as the brown chert or colorless quartz you mentioned, you are going to have to rely on solid provenance or laboratory testing (which indeed is sometimes done for things like archaeological finds and geological erratics to determine origin). Getting that experience is possible, and an enjoyable process for rockhounds. Go to any rock and gem shows that come to your area (or even travel to them when you have opportunity). Visit the deposits when you are in the area (even dig some if allowed). Go to local rock shops. Visit geology museums (some of which have also offered courses that will introduce you to some materials and how they formed). Join a rockhounding/lapidary club. Take an online gemology course. Lots of fun avenues to get there. edited to add: there be fakes and frauds out there - as there are with anything of value these days. Learning about those is also something that will stand you in good stead. Used to be that it was enough to be suspicious of certain things coming out of places like China and India, but the fraudsters now can disguise their actual location (or have hawkers in various other countries). I've had some of these myself (faked Owyhee jasper, fraudulent "Andesine," etc.) that were interesting to study. The Internet has been good in getting us more information conveniently, but also very bad in providing a wider market for the scamsters. In addition, lots of cutters and dealers (particularly in Asia) also seem to have only a vague idea of what it is they are selling - some buy in bulk, sell in bulk, and too often incorrectly state identifications and/or origins - not necessarily intentional fraud, but general carelessness by many, though by no means all.
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whyofquartz
spending too much on rocks
So, Africa is smaller than I expected...
Member since December 2019
Posts: 316
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Post by whyofquartz on Dec 14, 2019 13:30:00 GMT -5
Ok for example I can tell you that this is calcium suspended in a quartz matrix. But it is also seashells in (i think)agate. But does it have a name?
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Post by RocksInNJ on Dec 14, 2019 14:48:50 GMT -5
I’m lazy. I’d just call it caluarthellgate.
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fuss
spending too much on rocks
Member since October 2018
Posts: 250
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Post by fuss on Dec 14, 2019 16:39:32 GMT -5
Ok for example I can tell you that this is calcium suspended in a quartz matrix. But it is also seashells in (i think)agate. But does it have a name? That should likely just be called fossiliferous chert. If it becomes a really popular material that people want for lapidary/specimen purposes then a trade name could be created (usually location based).
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Post by rmf on Jan 2, 2020 22:00:04 GMT -5
whyofquartz First learn your minerals and there physical properties. A rock is composed of 1 or more minerals. The you will discover that info helps you learn rocks. Lapidary materials is a completely different thing. to a geologist it is quartz or chalcedony. to a Lapidary is is a Lake Superior Agate, Brazilian Agate, etc. Each agate type has a "look" or a range of appearance. A good example of a range of appearance is Monteczuma Agate. To a lapidary each location has a different name some are very diagnostic but some have a consistent appearance over a wide area. Study images of various cutting material, don't just look at them savor them.
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