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[Ru Smith]

And that had me looking again at the West Pasture crystal shown above. In that case the vivid green zone seems to be at a growth sector boundary.

[James Catmur]

Ru

I found the article and will read it this evening. Looks interesting, based on a quick glance

https://www.cas.miamioh.edu/~rakovajf/WTTW%20Sectoral%20Zoning%20Galley.pdf

[prcantos]

[Ru Smith]

Hi Pablo.

Attached is a small digression from fluorite - a Russian loparite penetration twin, viewed straight down the twin axis, still not ideal, but getting there.

But now we should probably get back to growth (concentric) and sectoral zoning in fluorites!

[Ru Smith]

I suppose another way to make a cruciform phantom, James, would be for an early cruciform group of parallel growth cubes (like the one shown in Fig 13 of Peter Megaw's article in Rocks & Minerals, 88, March/April 2013) to be engulfed by continued crystal growth.

[Ru Smith]

I tried photographing this one under water (Thanks Phil).

[Ru Smith]

This is a beautiful, luminous thing, but I'm going to have to try again to capture the colour zoning, from blue-green to dark blue to violet to green to white. It reminds me a bit of the sea off the Cape of Good Hope.

[Don Lum]

Ru,

There is a clear similarity.

Don

[James Catmur]

Ru

Looking carefully (the bottom left smaller crystal shows this well on the last photo) there is clearly some form of discontinuity/zone boundary running down the centre of each side of the crystal. So maybe if grew with that discontinuity between zones and that is where the colour is more intense?

James

[Ru Smith]

Hi Don,

Putting up the photos though I see that the fluorite has more green than that sea. I should have thought of something more tropical.

Here's a view of the reverse of the crystal, whch seems to be a complex contact. It gives an impression of the colour zoning - with plenty of backlighting.

[Ru Smith]

Interesting how the two faces on the Heights fluorite shown above sometimes grew at about the same rate, whereas at other times the left hand face grew faster. I've drawn the growth-sector boundary on the attached picture.