I was asking andrewbrown about the small stones we see selling from around the world and not having any clue as to how to choose a design...
... or the expectation of having a finished product of what... 50% of the size of the rough being optimistic?
50% yield from a specific piece of rough is generally very optimistic, generally only achievable if your rough has a freakily-good shape or has been pre-formed by the seller (rare) and would therefore command an extra premium in the asking price.
I think a 25 - 33% yield calculated over many cut stones seems to be closer to the average that normal facetors achieve. Carefully choosing a design to match the shape of your rough would get you closer to 33% average, with nice prismatic rough such as tourmaline crystals etc definitely helping in this regard. Highly irregularly-shaped rough with shallow projections usually means closer to the 25% yield, with unexpected inclusions discovered and requiring removal during the cutting process also affecting the final yield. Other factors such as human error while cutting can also combine to reduce the yield for a given stone, and affect your average too.
What kind of product to expect from a 2.5 carat sapphire or garnet... will wait for your experience... thaks.
So, bearing in mind all that, the answer to your question is unfortunately:
That depends....
If I was buying a 2.5ct piece of sapphire rough, I would be focussing on nice clean regularly-shaped offerings only, with the aim (hope?) of getting an 0.8ct finished stone.
RC
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