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EducationDolomite variety teruelite
15th May 2019 05:29 UTCErin Delventhal Manager
Is this term related to the crystal habit seen in these specimens rather than the color?
15th May 2019 05:52 UTCAlfredo Petrov Manager
Historically, the name came from the dolomites from Teruel, which have the characteristics of being dark (not necessarily "black", but grey and brown too), euhedral floaters, hosted in evaporitic gypsum and marl.
And then we have a red one, most likely colored by hematite inclusions (common in evaporites) right up there on top of the Mindat page where we call teruelites "black". Is that a teruelite too? Your opinion is as good as mine... The boundaries are fuzzy. (Sort of reminds me of our interminably debated "herkimer" definition... One eventually has to confess that the boundaries are fuzzy.)
Turns out that dolomite as dark brown to black(ish) floaters is quite characteristic of old evaporites, so I'd extend the "teruelite" classification to the dolomites from Chapare, Bolivia, too, as well as perhaps the ones from Hormuz island, Iran, although those have a flatter shape: https://www.mindat.org/photo-162676.html
Have I cleared anything up, or just muddied the waters?
15th May 2019 06:05 UTCErin Delventhal Manager
My reason for asking is that there is also a locality in New Mexico that produces what has, at least locally, been called teruelite. They're very similar to the "honey coloured" examples pictured from Spain. They are also euhedral floaters embedded in gypsum.
It seems to me that the definition we provide for teruelite ought be updated to not be defined by color, but by the geologic context.
I see no reason we can't mention that the original teruelites were black, but the current definition doesn't seem to give much information at all.
15th May 2019 06:28 UTCAlfredo Petrov Manager
Got any photos of your NM ones? I've always had a fondness for that evaporitic environment, underappreciated by many collectors.
Edit: Mindat seems to have just one photo of what we're talking about, from New Mexico: https://www.mindat.org/photo-322715.html
15th May 2019 07:29 UTCErin Delventhal Manager
Here are some more photos of the New Mexican dolomites - I'd like to add these to fill in alongside Dan's image, but I'd also like to have the matter of "teruelite"-or-not sorted out so I don't have to come back and fix them later. ;)
15th May 2019 07:51 UTCAlfredo Petrov Manager
We should probably remove the word "black" from the Mindat description; I've never seen one that was truly black. They seem to vary from light brown to dark brown to brownish grey to very dark brownish grey. Whoever wrote "black" was using the word a bit loosely and meant to say "dark".
15th May 2019 08:01 UTCErin Delventhal Manager
15th May 2019 08:25 UTCErik Vercammen Expert
15th May 2019 08:58 UTCErin Delventhal Manager
I could probably agree with the steep rhombohedron, but I'd raise some question over the pinacoid. At least per the New Mexican examples I've posted, they fit the steep rhombohedron, but I haven't noticed any with the pinacoid - does that point alone eliminate them from being considered teruelite, even if everything else fits?
15th May 2019 08:58 UTCJolyon Ralph Founder
Do NOT remove the word black please :)
15th May 2019 09:01 UTCErin Delventhal Manager
15th May 2019 10:16 UTCJolyon Ralph Founder
From 'The Mineral Collector (1898)"
15th May 2019 10:17 UTCJolyon Ralph Founder
I'm just going to leave that here.
15th May 2019 10:24 UTCJolyon Ralph Founder
Every early reference to the name Teurelite refers to the crystals being dark or black, found in gypsum-rich marls.
I think we need to keep the black/dark description, and we should remove the photos of dolomite that doesn't match.
When the name was given it was given for something quite specific. We do no favours to anyone by using the name for similar, but not identical, things.
15th May 2019 11:07 UTCErik Vercammen Expert
@Elvin: it was something that popped up from the depths of my memory, but I don't remember the source (and I'm even not 100% sure, that's why I wrote "i thought..."
15th May 2019 13:54 UTCTimothy Greenland
Cheers
Tim
15th May 2019 14:55 UTCTony Nikischer 🌟 Manager
15th May 2019 15:24 UTCJuan Miguel Casanova Expert
Como está Alfredo que sabe español escribo en español que me expreso mejor. Con la teruelita pasa algo parecido a los jacintos de compostela. Es una variedad que no está definida. Para mi las terueitas igual que los jacintos de compostela son una variedad de dolomita que aparece en los yesos y dolomías de las facies Keuper que se describió por primera vez en Teruel. Para los jacintos siempre ha estado la controversia del color, para algunos autores son sólo los de color rojo y para otros lo son todos a excepción de los negros. En el caso de las teruelitas no suele existir esta controversia sobre el color e incluso con el tipo de romboedro, lo habitual es el romboedro agudo. Pero sí, son negras, marrones, rojas e incoloras. El color más habitual es el negro.
15th May 2019 15:33 UTCJuan Miguel Casanova Expert
Estudio mineralógico de unas "teruelitas" del Keuper de la provincia de Castellón por DRX, SEM/TEM/EDX. ESTEVE, V.; SANFELIU, T.; REVENTÓS, M. M. & AMIGO, J. M. 1993, Boletín de la Sociedad Española de Mineralogía, 16, 1:49-50
Observaciones cristalográficas sobre la teruelita. CHAVES Y PÉREZ DEL PULGAR, F. 1891, Anales de la Sociedad Española de Historia Natural. Actas de la sesión celebrada el 4 de febrero, 20: 9-10
Sobre la estructura de la teruelita. MARTÍN CARDOSO, G. & GARRIDO, J. 1931, Boletín de la Real Sociedad Española de Historia Natural. (Notas y comunicaciones), 3 cuadr., 4 fig., lám. III y IV., 31: 379-398
La Teruelita. FERNÁNDEZ GALIANO, D., 1950, Teruel, 6 (12) 163-174
Hay más bibliografía
15th May 2019 16:48 UTCAlfredo Petrov Manager
And as our Spanish expert Juan Miguel states above, the variety was always considered poorly defined, even by the Spanish, being black, brown, red, and colorless, with black being the most common, and the most common habit being a sharp rhombohedron.
Juan Miguel, many thanks for the references. I have added them to the teruelite page.
15th May 2019 18:04 UTCPaul Brandes 🌟 Manager
15th May 2019 19:52 UTCErin Delventhal Manager
Given Juan Miguel’s description (thanks for that!) and comparison to the situation with the Jacintos del Compostela, it would seem to me that the important component of the definition is the geological context.
The utilitarian part of me would like to argue that the term “teruelite” is much more useful by that definition than by simply being “black dolomite.”
15th May 2019 20:18 UTCJolyon Ralph Founder
But if the name refers to black/dark crystals (as it certainly seems to do) then that wouldn't be true..
> called "absolutely black" looks dark chocolate brown to me when I look closely
True black doesn't really exist. Everything we call black is a very dark shade of something. But here's not the place to discuss the philosophy of colour but to accept in practical terms they would be described as 'black' by most people.
The term 'Black or dark coloured' works for me. Red crystals, that not the same thing. Light honey brown, not that either.
15th May 2019 21:31 UTCEd Clopton 🌟 Expert
With the discovery of similar dolomite crystals in identical environments in other localities since the "teruelite" name became established, it would make sense to define them in terms of the environment and crystal habit, and say that specimens from the "variety locality" of Teruela classically are black or nearly so but that brown, reddish, and honey-colored crystals are well known from Teruela and other localities.
15th May 2019 22:13 UTCJolyon Ralph Founder
> t would make sense to define them in terms of the environment and crystal habit, }
That's not how names work!
You might as well redefine amethyst to be any crystalline quartz found in volcanic cavities!
15th May 2019 22:17 UTCJolyon Ralph Founder
You can compare them to 'Teruelite', you can call them 'Teruelite-like' if you wish (in the description, not the species name). You can of course do whatever you want on your own labels.
15th May 2019 23:16 UTCErin Delventhal Manager
-------------------------------------------------------
> That's not how names work!
I would argue that this is exactly how names, and languages as a whole, work.
15th May 2019 23:40 UTCFrank K. Mazdab 🌟 Manager
15th May 2019 23:52 UTCJolyon Ralph Founder
I dislike seeing a name for what is quite an interesting variety of dolomite being diluted by people who have something *slightly* similar but not the same.
The original descriptions were clear on it being black or dark.
15th May 2019 23:54 UTCJolyon Ralph Founder
16th May 2019 00:13 UTCRalph S Bottrill 🌟 Manager
16th May 2019 02:12 UTCErin Delventhal Manager
16th May 2019 05:33 UTCGregg Little 🌟
It appears that that is exactly Ralph's, Jolyon's and others' point. Once the name encompasses a wide variety of characteristics, far from its original intent, then the name becomes useless. Languages do evolve around popular usage but minerals don't evolve. If a wide range of dolomite colours get lumped into Teruleite then Teruleite might as well be simply called dolomite.
This whole line of thinking takes me back to the earlier nonsensical discussions around "ruby" emerald.
16th May 2019 08:00 UTCErin Delventhal Manager
1) a limited late 1800s-early 1900s name for black dolomite - this is, in my opinion, utterly useless; or
2) a more modern and more encompassing usage of the term to refer to a very specific type of occurrence of dolomite that can result in different colors, but has a distinct geology AND similar crystallography - this is, in my opinion, actually a useful term.
16th May 2019 11:15 UTCBenjamin Oelkers
16th May 2019 13:20 UTCJolyon Ralph Founder
16th May 2019 14:33 UTCJuan Miguel Casanova Expert
16th May 2019 15:56 UTCDonald B Peck Expert
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: May 4, 2024 11:41:59