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Fossicking Locations / Re: Victorian Sapphires
« Last post by RoughCreations on Today at 10:51:40 AM »Thank you. And you would expect a 1mm finished jewel if all goes well?Hi Alaskan,
Remember that the final yield is a percentage of the original rough's weight, not width or other dimension.
For example, a 10mm diameter Standard Round Brilliant (SRB) sapphire would weigh about 3.65ct, a 9mm would be 2.66ct, an 8mm would be 1.87ct, a 7mm would be 1.25ct, and a 6mm 0.79ct and so on, according to my Gem Cut Studio size/yield calculator. So in this example, in going from 10mm to 7mm diameter, the carat weight has dropped to ~ one third. That is, the relationship between the width of a cut stone and its weight is not linear.
In other words, a spherical-shaped 3mm diameter (mythical) sapphire cutter found while fossicking would weigh about 0.3ct in its rough uncut form. If it was cut into a SRB, the best theoretical yield achievable would be a cut stone of 3mm diameter, weighing 0.1ct giving a yield of 33%.
In a more real-world scenario, where the 3mm rough sapphire cutter was a bit more irregular in shape, it would weigh a bit less than 0.3ct, and we may expect a yield closer to 25%, this would equate to perhaps a 2.7mm stone (.07ct) in our SRB example.
So, in summary, a 1mm finished jewel from a 3mm rough would be a bit disappointing! I reckon you could do better than that on a rainy day with good karma and a hot cup of cocoa, lol.
RC