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#1

Lefty
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Joined: 01 May 2014
Posts: 941
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04 December 2016 11:41 am

The traditional consensus is that there's not much you can do with those really, really super-dark blood red garnets. And within the normal faceting parameters, I've found that to be correct.

But I'm not ready to give up on them altogether. I still think they have potential if you think outside the box. Here is one that breaks the rules of faceting - it's basically a faceted-top cabochon with no pavilion, just a dead-flat bottom. Such a stone should be a total fish-eye according to conventional thinking - but it isn't. It is windowed to an extent but nonetheless, light entering the stone certainly does reflect back and in this case creates an interesting effect (difficult to really capture in a still photo), kind of like looking through a magnifying glass at a bunch of little lights arranged in a honeycomb pattern. This stone is much more lively than you would expect from something that totally violates the principle of critical angles!

31400128445_10fbb99dd7_c.jpg

The low crown without a pavilion, just a girdle about 1.5mm wide makes the stone thin and is necessary to allow light to penetrate the extremely heavily saturated red without extinction. Moving it around in different light sources, it's clear that most of the internal reflection is coming from light entering through the sides rather than straight down, which makes sense since light coming straight down would be passing straight through.

I think further experiments are warranted, perhaps a square stone with just four big reflectors as pavilion facets with a culet angle of say 10 or 15 or 20 degrees - a long way below critical but still well higher than the current 0 degrees. If a flat bottom is still reflecting some light than perhaps a hyper-shallow pavilion will reflect more again without making the stone to thick - the whole problem with super-saturated stones is that light doesn't make it through to the pavilion and back out through the crown again.

There may be hope yet for those garnets and sapphires that are so saturated that any normal design makes them appear black. You probably wouldn't flog them, they would have very little carat weight owing to being so thin - but if you can still use them in jewellery setting, why not?

8 users like this post: Wally69, fossickeract, silver, shivan, Heatho, AtomRat, Mungoman, ktmman

#2

Hoffs gold
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Joined: 04 May 2013
Posts: 18
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04 December 2016 01:18 pm

Great write up Lefty and great to see you trying to breathe life in to what were thought to be unworkable stones.


Minelab GPZ-7000, E-Trac, Pro-find-25, Wal-banker. www.TheBeardedProspectors.com Living in the best country in the world, so get out and enjoy it!

#3

Lefty
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Joined: 01 May 2014
Posts: 941
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04 December 2016 04:45 pm

Cheers mate smile A lot of people have collections of very dark rough material that after a few frustrating attemtps, most of us just give up on. We need to think outside the box here. Mind you, it might not work for other dark stones that have a lower RI than garnet and sapphire but things are worth a shot.

#4

Heatho
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From: Sydney, NSW
Joined: 29 April 2013
Posts: 8,999
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04 December 2016 05:09 pm

To be honest I don't mind dark stones Lefty, especially dark royal blue sapphires. I think you nailed that garnet, it looks fantastic. I wonder if playing with the angles in some step cut designs may achieve some more light reflection? Anyway I'm not a cutter and wouldn't really know. big_smile


Minelab GPX 5000, SDC2300, CTX3030, Pro-Find-25, patience, lot's of patience.

#5

Lefty
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Joined: 01 May 2014
Posts: 941
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04 December 2016 05:43 pm

Cheers Heatho. I did experiment with shallow step cuts and it does work to an extent but the light has to be hitting them just right, like it is in this one...

25286777043_740d607de1_c.jpg

From most angles it doesn't look like this unfortunately.

2 users like this post: silver, ktmman

#6

Heatho
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From: Sydney, NSW
Joined: 29 April 2013
Posts: 8,999
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04 December 2016 06:38 pm

Yeah, fair enough Lefty, still it's a good looking stone in my opinion even if not technically perfect.


Minelab GPX 5000, SDC2300, CTX3030, Pro-Find-25, patience, lot's of patience.

#7

Lefty
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Joined: 01 May 2014
Posts: 941
Member
04 December 2016 07:31 pm

Cheers Heatho - I hasten to add that I don't mind some very deep-coloured stones either. I'd just like to be able to get these things to show the intense red that they actually are when enough light can get into them.

1 user likes this post: Heatho
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