Talk:Fluorite

Fluorite image

The photograph of "Fluorite crystals" image:Fluorite_crystals_270x444.jpg actually shows cleaved fluorite octahedra. Dlloyd 21:36, 17 Aug 2004 (UTC)

Blue john redirect

I got to this page from a redirect via Blue John and whilst Blue John is Fluorite not all fluorite is Blue John. Given that Blue John can only be found in Castleton,Derbyshire - surely a distinction should be made? CustardJack 09:56, 21 Apr 2005 (UTC)

See Derbyshire Blue John. Dave.Dunford (talk) 20:23, 15 March 2012 (UTC)

Alternative images

• 
  Pig carved in fluorite, 5 cm (2 inches) long

Colour in Fluorites

You're correct, saying that "blue john only comes from Derbyshire" is a bit like saying "only Nestle make Nescafe" I don't think anyone has patented "blue John" as a trade mark, but that is what it effectively is.
Equivelant very dark blue banded fluorite has been known to come from china and the Romans may have sourced some from the arabian peninsula.
Colour in fluorites appears to have been the subject of much debate. Early theories that the dark blue colour of some Derbyshire fluorites was due to hydrocarbon inclusions now seems unlikely (although hydrocarbon traces are present in that area). More likely theories are for colour centres caused by excess calcium in the lattice.
This is in contrast to the traces of transition metal ions, thought to colour most other minerals.
Dark blue colour in fluorite can be produced by x-ray or Gamma ray bombardment. (FW Smith, PHD Thesis, University of Durham (date?))this causes lattice deffects.
This may explain why some natural crystals only have a thin skin of dark blue; The mines and show caves around Castleton in Derbyshire have carefully monitored ventilation systems to control radon gas levels, which in some of the wild caves in the area can give a years recommended max exposure for a human in a few hours. this may over a long period give some lattice damage and colouring.
The delicate greens yellows and blues in English North Pennine fluorite may be due to rare earth metal traces causing lattice deffects, Prizibram, some time in the 1960's or 70's reported rare earth spectra from a specimen from Ramshaw Mine in Co Durham. FW (Rick) Smith found that Yttrium concentration increased towards vein intersections which were suspected feeder channels to the mineralisation (fluid inclusion hommogenization temperatures also followed this trend). Ixer appears to have done considerable research into trace quantities of rare earth minerals present in the north pennine mineralization.
Annealing of the crystal will destroy the colour in fluorites.
Some of the colours in North Pennine fluorites are meta-stable, for example, some (?most) green fluorites from this area will slowly change to mauve/ purple colour with exposure to sunlight.
-- unsigned by 194.106.142.221 (talk) at 18:35, 27 June 2007

Optics of Fluorite

My understanding of the reason for using fluorite in visible light optics is that it is:
1) cubic and therfore optically isotropic (only single refractive index)
2) it offered a third refractive index/dispersion combination, so that when combined in an "Apochromatic Triplet" with the conventional "flint" and "crown" type optical glasses, it allowed Red, Green and Blue light to be brought into focus on the same plane("apo-chromatic correction"), where using the conventional Achromatic double only two colours could be brought into focus on the same plane, the others focusing either infront or behind it.
I gather that the same correction effect can be achieved by leaving an air gap in a "doublet" so effectively creating an "air element".
3) it was available in clear, relatively colourless and relatively insoluble (in water)crystals.
The refractive index of fluorite is surprisingly low. In microscopic examination this causes fluorite grains in thin sections to stand out with high relief boundary contacts against the cementing medium used to mount the slide, and most other minerals, due to the fluorite having a significantly lower refractive index.
This low refractive index can be used to "look into" a scratched or worn specimen, as submerging it in water, especially salty or sugary water will surpress many of the surface reflections.
Apparently, the mineral cryolite has approximately the same refractive index as water, and gives the illusion of disappearing when submerged.
-- unsigned by 194.106.142.221 (talk) at 18:57_59, 27 June 2007

The article currently says:
"fluorite lenses have low dispersion, so lenses made from it exhibit less chromatic aberration, making them valuable in microscopes and telescopes."
While the low dispersion may be of interest in some special cases, like what above IP says about grains in microscopic slides, but I disagree that a *low* dispersion is what makes them valuable for telescopes and other optics. I believe it's just the fact that the dispersion is much *different* from that of glasses, so that in the combination of several different materials you get improved color correction, like what above IP says about the apochromatic triplet.
--BjKa (talk) 12:38, 14 February 2018 (UTC)

Blue John

Under the Blue John section it says "Recent deposits in China have produced fluorite with coloring and banding similar to the classic Blue John stone" Should that read "recently discovered deposits"? Richerman (talk) 16:31, 24 June 2009 (UTC)

Yes I'm sure it should. I've made the change. And because it is a separate location, I've also made it a separate paragraph. Feline Hymnic (talk) 18:51, 25 June 2009 (UTC)

Fluorite WRONG

I can't understand the apparently universal use of this term (fluorite) for CaF2. The suffix -ite is a strict chemical notation indicating the inclusion of oxygen atoms in the radical. Calcium Fluorite would be CaOF, a rather interesting compound!; Fluorate would imply "more" oxygen, and might exist as a perchlorate ie CaFO4 (Explosive?). Consider nitrate, nitrite or sulphate, sulphite, for other examples. We don't talk about salt as "sodium chlorite". That would be more or less bleach, not what we eat. So everywhere in the literature where they call fluorspar calcium fluorite, they should simply say, calcium fluoride. I'm not going to alter this because I've learned some people get upset but I do invite editors to reflect on this solepsism. PS I also agree that Blue John is a near unique mix even if CaF2 is widespread. —Preceding unsigned comment added by 86.152.10.122 (talk) 10:13, 30 September 2009 (UTC)

This would be an understandable complaint if it were regarding a man made chemical. However as this is a naturally occurring, crystalline, substance with a unique formula, it falls under the oversight of the IMA. As with most minerals described before 1959 and all minerals described after 1958, they are given official names with the -ite ending to identify them as minerals and not elements, or other substances. --Kevmin (talk) 10:45, 30 September 2009 (UTC)

There's nothing wrong with the term 'fluorite'. The names of most minerals end in -ite, see the article Mineral for plenty of examples. The Oxford English Dictionary definition describes one of the meanings of the suffix -ite as "The systematic ending of the names of mineral species".

See also Chlorite group for a group of minerals termed 'chlorites', yet not containing any chlorite ions.

The systematic name calcium fluorite implies Ca(FO₂)₂, composed of Ca²⁺ and the fluorite anion FO₂⁻, which is unknown. Compare this with the chlorite anion, ClO₂⁻, found in sodium chlorite, NaClO₂, for example.

Ben (talk) 11:03, 30 September 2009 (UTC)

Uses

At the end of the uses section the text says something like strong hexagonal crystal structure. Normally this mineral is considered to be brittle and the crystal structure is not hexagonal but cubic! —Preceding unsigned comment added by 150.227.15.253 (talk) 12:52, 22 March 2010 (UTC)

Antifluorite section?

There should be a section on antifluorite structure if "antifluorite" redirects to this page. 69.181.153.214 (talk) 05:03, 22 January 2012 (UTC)

Anti-fluorite really seems to have nothing to do with fluorite. It's just a type of crystal structure where the cations and anions are reversed from the CaF2 structure. Li2O, Na2O, K2O, UO2, ThO2 and Be2C are examples. I suppose it deserves its own page if someone out there knows more than me. Pelirojopajaro (talk) 14:22, 31 October 2019 (UTC)

See Anti-structure, to which Antifluorite directs now.--Smokefoot (talk) 17:01, 31 October 2019 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Fluorite/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Comment(s)

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The article is currently given low importance and concentrates on gemology / jewellry Fluorite / fluorspar is an important (strategic?), internationally traded industrial mineral commodity. Importance of article should therefore be up graded The world market price is currently set by china, and with reduced supply from china, global prices are currently rising as users seek secure supplies. It is currently the major source of fluorine and fluorides. Brief (and incomplete)list of uses: production of synthetic cryolite for aluminium smelting Flux in metal smelting and (occasionally)in cement manufacture hydrofluoric acid, used for etching, cleaning metals, as reagent in analytical chemistry Fluorocarbon plastics and rubbers e.g. Viathon & PTFE Enrichment of uranium (UF6) Refrigerant and propellant gasses Aneasthetics SSRI Anti depressants Fluorides used in anti refflective coating of lenses optical grade fluorite is used in optics for UV and in apochromatic correction of lenses.

Last edited at 17:23, 27 June 2007 (UTC). Substituted at 15:18, 29 April 2016 (UTC)

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Another "use"?

Fluorite as a raw material is used to produce one of the materials in solar photo-voltaic panels, although I know nothing of the details. Now well into 2024, is there enough world wide usage for this purpose to warrant a mention? 2001:8003:E40F:9601:5C39:E04:5AE1:26F9 (talk) 09:16, 7 April 2024 (UTC)