- Joined
- Aug 15, 2000
- Messages
- 18,492
David have you ever run a 60% table and 60% depth through HCA?
You will find we agree.
I just punched in a 31 degree crown and 41 degree pavilion - HCA 1.6, C34.5 P40.7 gives HCA 1.2 and C38 P40 gives HCA 1.6.
I do not think we need to argue about that.
But many 60:60 stones have slightly shallow crowns combined with fairly deep pavilions - The GIA found in a survey of 67,621 that 29% had table sizes 61 to 63%, crowns from 31 to 35.9 and pavilion angles from 41 to 42.4. Maybe 2% of those stones fall into Good HCA ranges
I have graphed the data from this GIA info and, assuming normal distributions, a typical crown and pavilion for a 60% table, 60% depth with a thin to medium girdle would be around 34 crown and 41.5 pavilion. When we look at typical GIA graded stones this is in fact what we see - it is also a sweet spot for cutters to maximise yeild and produce stuff the market accepts.
Now i take my hat of to you and others who maybe avoid this ''typical'' rubbish David. But you know how to avoid it - consumers do not.
You will find we agree.
I just punched in a 31 degree crown and 41 degree pavilion - HCA 1.6, C34.5 P40.7 gives HCA 1.2 and C38 P40 gives HCA 1.6.
I do not think we need to argue about that.
But many 60:60 stones have slightly shallow crowns combined with fairly deep pavilions - The GIA found in a survey of 67,621 that 29% had table sizes 61 to 63%, crowns from 31 to 35.9 and pavilion angles from 41 to 42.4. Maybe 2% of those stones fall into Good HCA ranges
I have graphed the data from this GIA info and, assuming normal distributions, a typical crown and pavilion for a 60% table, 60% depth with a thin to medium girdle would be around 34 crown and 41.5 pavilion. When we look at typical GIA graded stones this is in fact what we see - it is also a sweet spot for cutters to maximise yeild and produce stuff the market accepts.
Now i take my hat of to you and others who maybe avoid this ''typical'' rubbish David. But you know how to avoid it - consumers do not.