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The information provided within this Forum about localities is only given to allow reference to them. Any visit to any of the localities requires you to obtain full permission and relevant information prior to your visit. FMF is strictly against any illicit activities related to collecting minerals.
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| Search found 790 matches |
| Author | Message |
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 Topic: Need to identify strong green crystal |
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| alfredo Replies: 2 Views: 116 |
 Forum: FOR BEGINNERS: What is it? Where is it from? Posted: Sep 02, 2025 00:14 Subject: Re: Need to identify strong green crystal |
| Most probably it is quartz.
The title of your post refers to a "strong green" crystal, but I do not see any green crystals in the photo. |
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| Topic: Help identification |
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| alfredo Replies: 6 Views: 1809 |
Forum: What is it? - Where is it from? Posted: Aug 17, 2025 12:01 Subject: Re: Help identification |
| Yes, this is almost certainly hematite.
I don't put too much emphasis on hardness testing - It is just too easy to do them wrong. Measuring density is a more definitive test for amateurs when a sam ... |
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| Topic: Help identification |
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| alfredo Replies: 6 Views: 1809 |
Forum: What is it? - Where is it from? Posted: Aug 16, 2025 15:34 Subject: Re: Help identification |
| What is the color of the powder when you rub it on a piece of broken porcelain? | |
| Topic: The most over-rated/overpriced species??? |
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| alfredo Replies: 7 Views: 2361 |
Forum: Minerals and Mineralogy Posted: Aug 11, 2025 10:09 Subject: Re: The most over-rated/overpriced species??? |
| Humans are so easily influenced by "fashion", and stones go through fashions just like clothes and art do. Tourmaline and moldavites are examples of things which some "influencers" ... | |
| Topic: Researching location information for old specimens. |
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| alfredo Replies: 5 Views: 1482 |
Forum: The histories behind mineral specimens Posted: Aug 10, 2025 13:45 Subject: Re: Researching location information for old specimens. |
| A great example, Jesse, thanks to your research, of "unwarranted specificity"! Collectors (and consequently dealers) seem to feel a lot of pressure to have a mine name for each specimen. We ... | |
| Topic: Libyan Desert Glass Structure |
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| alfredo Replies: 71 Views: 101222 |
Forum: Minerals and Mineralogy Posted: Jul 25, 2025 15:22 Subject: Re: Libyan Desert Glass Structure |
| Ammonium bifluoride solution in water. It will dissolve the fine-grained silica, but attack the coarser stuff much more slowly. So, if you time it right by checking frequently, you can increase the co ... | |
| Topic: Libyan Desert Glass Structure |
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| alfredo Replies: 71 Views: 101222 |
Forum: Minerals and Mineralogy Posted: Jul 01, 2025 14:47 Subject: Re: Libyan Desert Glass Structure |
| Marco wrote: " you cannot hunt for fossils inside a glass that was formed at temperatures estimated to be above 2750°C. If the rocks around the impact have been sublimated you cannot find any tra ... | |
| Topic: Preparing a list of light sensitive minerals - (14) |
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| alfredo Replies: 97 Views: 221616 |
Forum: Featured Columns of FMF Posted: May 21, 2025 16:53 Subject: Re: Preparing a list of light sensitive minerals - (14) |
| José Angel, In the case of your coquimbite turning brown, it is not the light but rather the dryness that is the problem. Coquimbite is only stable at atmospheric humidities between 30 < 70 %. Drie ... | |
| Topic: Star Quartz |
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| alfredo Replies: 3 Views: 6429 |
Forum: Micros & Macros - Images of Minerals Posted: Apr 19, 2025 11:21 Subject: Re: Star Quartz |
| This is a piece of star quartz I got at the Prague show several years ago. Seems to have started growth as quartz with red hematite inclusions, and later continued growth as yellow quartz with probabl ... | |
| Topic: cristobalite vs chalcedony in thin section |
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| alfredo Replies: 16 Views: 23351 |
Forum: Minerals and Mineralogy Posted: Apr 09, 2025 13:18 Subject: Re: cristobalite vs chalcedony in thin section |
| Hi Alfredo,
perhaps you are referring to the gypsum of Mina Rica, Pulpì, Almeria... Hi Marco, No, I have never been to Pulpi, or anywhere else in Almería. Definitely gypsum beds in Archidona, wh ... |
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| Topic: cristobalite vs chalcedony in thin section |
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| alfredo Replies: 16 Views: 23351 |
Forum: Minerals and Mineralogy Posted: Apr 08, 2025 21:34 Subject: Re: cristobalite vs chalcedony in thin section |
| Thank you, gentlemen, for this interesting discussion. I observed very similar looking millimeter-size spherules in gypsum in Archidona, Spain: https://www.mindat.org/loc-257672.html - and I had been ... | |
| Topic: Wulfenite and Mimetite |
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| alfredo Replies: 17 Views: 193258 |
Forum: Micros & Macros - Images of Minerals Posted: Apr 06, 2025 01:29 Subject: Re: Wulfenite and Mimetite |
| You don't need acid to dissolve fluorite, because fluorite is very slightly soluble in plain water! ...a few tens of milligrams per liter of water. So if you put a fluorite crystal into running water, ... | |
| Topic: Wulfenite and Mimetite |
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| alfredo Replies: 17 Views: 193258 |
Forum: Micros & Macros - Images of Minerals Posted: Apr 04, 2025 19:09 Subject: Re: Wulfenite and Mimetite |
| "the limonite is not replacing the fluorite, so not a pseudomorph"
Some pseudomorph collectors would disagree with this statement and would consider these "moulds" to be one of ... |
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| Topic: Libyan Desert Glass Structure |
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| alfredo Replies: 71 Views: 101222 |
Forum: Minerals and Mineralogy Posted: Mar 19, 2025 11:54 Subject: Re: Libyan Desert Glass Structure |
| Sorry, I just accidentally deleted someone's post here. If it was yours, please re-post it. The post appeared double on my screen, so I wanted to remove the duplicate, but they both disappeared. Must ... | |
| Topic: Libyan Desert Glass Structure |
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| alfredo Replies: 71 Views: 101222 |
Forum: Minerals and Mineralogy Posted: Mar 18, 2025 03:10 Subject: Re: Libyan Desert Glass Structure |
| Marco, thank you for this very interesting explanation.
I'm wondering what you mean by "anhydrous" magma yielding obsidian, because obsidian does contain a little bit of water. One common ... |
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