FMF - Friends of Minerals Forum, discussion and message board

[John Medici]

Sorry, I missed labeling a dodecahedron face, between the tetrahex faces on my Bluffton specimen (my number 006).

[nurbo]

Here is one from the California Mine in Teesdale, it seems these are rare but widespread in the North of England, when I get a chance I'll be checking all my Fluorite's for these modifications, The crystal in the second photo seems to have a further modification which is quite hard to see in the picture so Ive cobbled together a drawing which is inaccurate but shows what it looks like.

[Ru Smith]

Great stuff, nurbo.

So, you have found another example with both trapezohedron and hexoctahedron showing. Do any of yours have a little triangular facet right at the corner (the octahedron)?

[nurbo]

Hi Ru,
If i'm understanding you correctly yes, i've a few with the octahedron,and some Galena's that show it too, Im really glad you started this thread, it made me remember the edges on this one and set me off trying to find it I couldnt remember the locality either, eventually I found it in with the samples I have for trading or giving to people.

a couple of observation's on the California Mine piece ... the Fluorite cube's with the trapezohedral modification are an earlier generation than the the ones with both,trapezohedral and hexoctahedral, i also noticed that the trapezohedral modifications are present on the raised edges on the face of the first generation of cubes as well, when the sun comes back up I'll try and get some better photo's.

[Antonio Alcaide]

Nice complex fluorites. More complexity here https://www.foro-minerales.com/forum/viewtopic.php?p=70706#70706

in Spanish, with deeply complex crystals from Cillargas, Spain (in the link) and Jaimina Mine, Asturias, Spain (more hexoctahedra called hexaquisoctahedra in Europe) as well as tetrahexahedron on a Naica specimen, as Ru commented (see the previous posts).

Regards

[Ru Smith]

Excelente Antonio! Gracias.

I made a drawing of the Great Sleddale crystal corner. Can anyone identify the green faces?

[Ru Smith]

Also interesting to see is that there's a textural difference to the hexoctahedral faces and there's a subtle angle change within the H field of the drawing which I chose not to show - it's complicated enough as is!

[nurbo]

[Jordi Fabre]

[Ru Smith]

Thanks Jordi. There are some very interesting crystals in those links.

Yes, nurbo, the red face is the octahedron. So what else did you come across in your look through those northern fluorites?

[nurbo]

Hi Ru,
I didnt realise you meant the octahedron could form on top of the other two modifications, its pretty obvious I suppose, but sometimes I can be thick :-)

I looked through about 50 or 60 samples and found one or two that hint at these modifications but I'm not sure if it's more down to slight deformities in the lamellar structure of the cubes. rather than actual bona fide modifications,

I might go and look through my friends collection, and see if he has any.. I cant help thinking about those Fluorite's from the Schlucht valley in Germany, the ones with 54 faces., I've got a couple of micro's but I dont think my old camera is going to get a decent photo of them, I'll have a go at it but if can anyone else chip in with one, that'd be good.

[Ru Smith]

So, I came across a little (3 mm) blue cube with tetrahexahedron (double bevels on the edges) on specularite from the Florence Mine, the only one I have seen so far.

[Ru Smith]

Too much depth of field doesn't help with these pictures since the crystals are transparent, so here's that crystal again, with only the shallowest few photos stacked.

[Ru Smith]

and today I found some nice examples from the Hollywell Mine (Co Durham) showing the tetrahexahedron. Looking definitely helps with seeing.

[nurbo]

Hi Ru,
Out of interest do you find that on these pieces the modifications are present on every cube, just the odd one or as I found on the California Mine piece, different for different generations of crystallization ? Ive been too busy with work to get around to continuing my hunt for these modifications, Im hopeful that at the weekend I may continue the quest.

Great photo's by the way.