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Yep mostly from the Frome River a few years ago when my back was still capable of digging.
⭐ Gemstone & Mineral Show n Tell
- Thread starter Colin&Lee
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This one is 1.1ct found at grabben gullen
These two are 3ct and 1.3ct
What do you guys think? are these considered quality sapphires? The 1.3ct last photo Is actually quite a baby aqua colour doesn't show thru photo.
I think they look good haha but I'm not sure what denotes good quality
These two are 3ct and 1.3ct
What do you guys think? are these considered quality sapphires? The 1.3ct last photo Is actually quite a baby aqua colour doesn't show thru photo.
I think they look good haha but I'm not sure what denotes good quality
You often have to polish a small window so you're not looking through rumbled surfaces to see what's inside; silk, fractures etc. Size obviously has a major impact, but clarity and colour are important factors as is the overall shape.
A well shaped piece of rough, by that I mean a piece where the overall shape suits a particular finished shape, ie round, octagonal, triangular or rectangular will lose upto 80% of it's weight during cutting, badly shaped even more so, this has a major impact of 'quality', so your 1.3ct rough could produce a 0.25ct stone, and that's tiny and to be totally honest a PIA to cut, though some cutters specialise in small stones, 3 - 4ct is pretty much my minimum rough size.
A 1.3ct colourful rough I would consider better for direct casting into a piece of 'organic' style jewellery styled around different colourful rough, and any serious gem fossicker probably has jars or stones like these. Sand casting rough stone jewellery in silver is an area I would like to explore as I think they would sell well and it's a good way of value adding these sort of stones if you have the market.
I hope this goes a little way to answering your question, the stone I'm seeing looks reasonably clean, the browner end looks to possibly have a fracture line in Pic #3 & 4, but there might be a little trillion in the blue end.
A well shaped piece of rough, by that I mean a piece where the overall shape suits a particular finished shape, ie round, octagonal, triangular or rectangular will lose upto 80% of it's weight during cutting, badly shaped even more so, this has a major impact of 'quality', so your 1.3ct rough could produce a 0.25ct stone, and that's tiny and to be totally honest a PIA to cut, though some cutters specialise in small stones, 3 - 4ct is pretty much my minimum rough size.
A 1.3ct colourful rough I would consider better for direct casting into a piece of 'organic' style jewellery styled around different colourful rough, and any serious gem fossicker probably has jars or stones like these. Sand casting rough stone jewellery in silver is an area I would like to explore as I think they would sell well and it's a good way of value adding these sort of stones if you have the market.
I hope this goes a little way to answering your question, the stone I'm seeing looks reasonably clean, the browner end looks to possibly have a fracture line in Pic #3 & 4, but there might be a little trillion in the blue end.
Yes it does dihusky, thank you for spending the time to write this.
Really, 80%? I was under the impression from what I've read something like 25-50% max, stone dependent.
Really, 80%? I was under the impression from what I've read something like 25-50% max, stone dependent.
This stone here started out as a 5ct rough, it was a bit of an odd shape but very clean, weighs about 0.9ct now but it's a lovely stone and was well worth having cut. This is why a finished gem is valuable as only about 5% of stones found if your lucky are worth cutting and are true gem quality, maybe only 1% sometimes.
Here's another 5ct stone that ended up about 0.9ct as well. Top quality but ended up a tad dark but these are they types of stones you're after that will cut nicely
Here's another 5ct stone that ended up about 0.9ct as well. Top quality but ended up a tad dark but these are they types of stones you're after that will cut nicely
Kotolos said:
At times I wish it were 25-50%, watching a lovely piece of rough sitting as powder in the bottom of a bucket is never nice, but when you look at a faceting diagram and compare the start to the finished, you'll understand why 80% is what it is.
To help, this is probably a good example, a round stone with fairly standard proportions, superimpose this on a piece of rough and see how much excess has to be cut off.
The overall shape is like the stone Heatho is showing, just the cut is very different. And all it takes is for a little divot that doesn't vanish in the first cut and the finished target starts to shrink, or one cuts the pavilion (the point side) and discover there isn't enough material to cut the crown, so the stone shrinks a bit further.
The 80% often comes as a shock to a fossicker excited with their finds, but it is what it is. I think my best loss has been around 65% but that's incredibly rare unless the stone is being cut free-form. Some people say.. what if you change the angles? But the angles are critical element and all relate to the Refractive Index (RI) of the stone and how well the stone will 'dance' when finished. Get them wrong and the stone either goes black or turns like coloured glass (windowing).
This explains it well:
The good, the bad & the ugly.
Does that loss apply to the Asian cutters as well mate? Just wondering.
Cheers
Mackka
Cheers
Mackka
Very interesting dihusky, thank you.
Looking at those images its clear how a lot of volume is lost around the pavilion and the additional for the crown and the rest add up.
In regards to the refraction, that must be another important reason to make sure the person cutting is reputable?
Does anyone have any photos of cutting fails of the refraction angles?
How manys cts (approx range like 10ct? 30ct?) does one that is pretty good shape have to be to cut like 4ct +
Looking at those images its clear how a lot of volume is lost around the pavilion and the additional for the crown and the rest add up.
In regards to the refraction, that must be another important reason to make sure the person cutting is reputable?
Does anyone have any photos of cutting fails of the refraction angles?
How manys cts (approx range like 10ct? 30ct?) does one that is pretty good shape have to be to cut like 4ct +
In certain larger sapphires or zircon etc. if the shape permits, can the larger parts that get cut off around the pavillion be used to facet itself? is that a thing?
Mackka said:
From the 'native' cuts I have seen, the finished cuts are very obviously based on carat yield not on accurate angles, many tend to have bulky pavilions with a lot of little facets, but weigh more than what a precision cut stone would. The Thai jam peg machines are good for fast repeatable cutting by a skilled operator, but they don't have a precision angle setup, not a multiple index system, the index is something like a plastic octagon with the dop/peg wedged in with some paper and the finished angle is determined by the depth of cut.
I've got a couple of native cut stones which I bought specifically for re-cutting and to use as an example of how different the same stone can look following a precision cut. I'll get them cut once I've finished the latest batch of Sapphires and post the before and afters.
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