FMF - Friends of Minerals Forum, discussion and message board

[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.

[Ru Smith]

Thanks nurbo,

It varies. I only found one crystal showing the edge modifications on the Ullcoats specimen, whereas most of the Hollywell crystals on that specimen show them - and none of my other Hollywell specimens show any edge or corner modifications at all.

[nurbo]

I discovered 2 more yesterday, one on a sample from Birkett Common in Cumbria and one on a sample i got at Bakewell for £1 labelled "Cowshill" which is a village in Weardale, i'll see if I can get that locality sorted out and get some photo's up in the next couple of days.

[Ru Smith]

Looking forward to the photos, nurbo!

[nurbo]

"A couple of days" hmmm! well 14 :-)

Here is the Birkett Common piece, the Cowshill piece and a Florence Mine piece I've photographed with these modifications. though Im not sure about the Birkett Common one, the curvature at the edges makes me wonder though. The Florence piece is a bit hard to make out, its where the light reflected off the edge I was trying to capture, slightly to the left of centre just above the middle..

[Ru Smith]

Great stuff, nurbo. Good to see these.