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Don Lum
Joined: 03 Sep 2012
Posts: 2861
Location: Arkansas
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Posted: May 19, 2013 00:03 Post subject: Re: When can a fossil be also considered a mineral? |
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"Knowledge is knowing the tomato is a fruit, wisdom is not putting in your fruit salad.”
Miles Kington
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Carles Millan
Site Admin
Joined: 05 May 2007
Posts: 1474
Location: Catalonia
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Posted: May 19, 2013 15:00 Post subject: Re: When can a fossil be also considered a mineral? |
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Don Lum wrote: | "Knowledge is knowing the tomato is a fruit, wisdom is not putting in your fruit salad.” Miles Kington |
I fully agree (exactly the same is valid for avocados, isn't it?).
And going back to the topic, strangely enough Mindat, by way of the admired and respected Rock Currier, admits Pyrite after ammonite as if it were a regular mineral specimen. And it is nothing less than from the collection of the Smithsonian Institute.
Photo copyright © Rock Currier, downloaded from Mindat.org - Creative Commons Attribution Licence - Some Rights Reserved.
Description: |
Pyrite after ammonite. Middle to late Jurassic. Specimen is from the collection of the Smithsonian Institute, Museum of Natural History #123770 (1973). Scale at bottom of image is an inch with a rule at one cm. From Le Clapier, Cornus, Aveyron, Midi-Pyrénées, France |
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Carles Curto
Joined: 14 Sep 2006
Posts: 160
Location: Barcelona
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Posted: May 20, 2013 01:12 Post subject: Re: When can a fossil be also considered a mineral? |
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Pyritized fossils (why not opalized fossils, i.e?) were usually admitted in most of the collections in the XIX and XX centuries. Currently, they are not so commonly included.
Some peripheral aspects of the mineralogy, as artificial and synthetic material, faceted and polished minerals, mining lamps and artifacts, old (or modern) photos and other documents, stamps… are freely added to the any collection.
I want especially note this aspect of “freely collecting”. Anybody having his own baggage of knowledge, aesthetic perception, interest, etc., the most important is to enjoy collecting, so, admit some “clearly mineralized” fossils in the collection must be a personal election, not a rule.
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Carles Millan
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Joined: 05 May 2007
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Posted: May 20, 2013 09:02 Post subject: Re: When can a fossil be also considered a mineral? |
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Carles Curto wrote: | (...) the most important is to enjoy collecting, so, admid some “clearly mineralized” fossils in the collection must be a personal election, not a rule. |
A very reasonable answer. All collectors are free to assemble their collection the way they like more. No questions asked.
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Singingstone48
Joined: 05 Feb 2009
Posts: 19
Location: Houston, Texas
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Posted: Jul 23, 2013 14:26 Post subject: Re: When can a fossil be also considered a mineral? |
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Carles,
Here are a couple examples from my own collection. I collected a bryozoan fossil from an outcrop near Kansas City. Bryozoans normally coat other objects on the seafloor. I accidently dropped it, and one corner broke off. When I looked inside I could see the internal structures of a brachiopod which had re-crystallized as calcite rhombs. Sitting in the middle of this hollow space was a 2 cm long white calcite scalenohedron. So this is a case of a fossil on a fossil with a mineral inside. Second, when I was in graduate school in Indiana I collected geodes near Bloomington. Often they were recognizable as crinoids, corals or brachiopods, but they were still geodes with interesting quartz crystals and occasionally calcite or Baryte inside.
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Bob Harman
Joined: 06 Nov 2015
Posts: 765
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Posted: Apr 19, 2020 22:05 Post subject: Re: When can a fossil be also considered a mineral? |
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A very old thread is resurrected. A nice example of what Steve was referring to in his last post of 2013.
Quartz replacing a fossil brachiopod from Monroe County Indiana.
This is the rare "dewdrop diamond" variant as individual smoky quartz crystals
sparkle like dewdrops in bright sunlight. Bob
Mineral: | Quartz replacing a fossil brachiopod |
Locality: | Monroe County, Indiana, USA | |
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Dimensions: | 7.5 cm |
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Mineral: | Crystalline quartz (var smoky quartz) on microcrystalline quartz (var chalcedony) |
Locality: | Monroe County, Indiana, USA | |
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Dimensions: | 7.5 cm |
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David K. Joyce
Joined: 15 Dec 2018
Posts: 20
Location: Canada
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Posted: Apr 20, 2020 08:02 Post subject: Re: When can a fossil be also considered a mineral? |
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Here is a mineral specimen disguised as a fossil. A gastropod, I think. It is as thin as an eggshell and totally composed of tiny calcite or dolomite crystals.
Mineral: | Calcite |
Locality: | Amherstburg (Amherstberg), Essex County, Ontario, Canada | |
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Dimensions: | 30mm |
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Gastropod composed of tiny calcite crystals |
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Scot Krueger
Joined: 02 Feb 2019
Posts: 11
Location: Massachusetts
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Posted: Apr 20, 2020 16:21 Post subject: Re: When can a fossil be also considered a mineral? |
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I had to ask myself the question many times when I decided to finally create a formal catalog of my collection. Since I have collected both fossils and minerals my whole life, I have many of both. So it was natural to create a flag in the database to declare whether a sample was a "fossil" or a "mineral" (or a rock, or jewelry, etc.). But I found there were a handful of examples that could easily fit either category. The attached photo is one such example. It is a fossil clam from Florida which is lined with beautiful golden calcite crystals. I finally decided the question by asking myself, if I had to house my fossils and my minerals in different buildings, which building would I put this in? Since I had bought it at the Tucson Gem and Mineral Show because I loved the golden calcites, I decided this one was a mineral specimen. But I have other, self-collected fossils which have calcites in the void space that are far from aesthetic enough to raise the question, and those I kept primarily as fossils, so they got the fossil tag.
Mineral: | Calcite |
Locality: | Ruck's pit, Fort Drum, Okeechobee County, Florida, USA | |
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Dimensions: | 10.5 cm |
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Golden calcite in fossil clam (Mercernaria sp.) from Florida. |
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R Saunders
Joined: 28 Jul 2018
Posts: 126
Location: Michigan
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Posted: Apr 20, 2020 16:35 Post subject: Re: When can a fossil be also considered a mineral? |
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Mercernaria sp. means edible Mollusk. Former Ruck's itt quarry, now closed to collecting.
Mineral: | Mercernaria sp. |
Locality: | Ruck's pit, Fort Drum, Okeechobee County, Florida, USA | |
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Mineral: | Mercernaria sp. |
Locality: | Ruck's pit, Fort Drum, Okeechobee County, Florida, USA | |
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Bob Harman
Joined: 06 Nov 2015
Posts: 765
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Posted: Apr 20, 2020 16:50 Post subject: Re: When can a fossil be also considered a mineral? |
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Scott's example and R Saunder's examples are minerals associated with fossils.
Calcite crystals associated with clam shell fossils from Ruck's pit in Florida.
Mine and David J's are quartz or calcite replacing the fossil.
The association of the 2 or the replacement by one of the other are 2 very different processes.
The original posting was what to call the example: fossil or mineral.
With the association of the 2, there is both a mineral and the fossil, not one or the other. Bob
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R Saunders
Joined: 28 Jul 2018
Posts: 126
Location: Michigan
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Posted: Apr 20, 2020 17:21 Post subject: Re: When can a fossil be also considered a mineral? |
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Bob Harman wrote: | Scott's example and R Saunder's examples are minerals associated with fossils.
Calcite crystals associated with clam shell fossils from Ruck's pit in Florida.
Mine and David J's are quartz or calcite replacing the fossil.
The association of the 2 or the replacement by one of the other are 2 very different processes.
The original posting was what to call the example: fossil or mineral.
With the association of the 2, there is both a mineral and the fossil, not one or the other. Bob |
Bob, both of mine came from a man thinning out his collection. One was in a free rock pile. Any idea which came first, the yellow calcite then the Mollusk settled over it or did the calcite from in the shell remains? or any body's guess?
Bob Saunders
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