Frome River Sapphires

I have been provided with some sapphires from the Frome/Weld River area (NE Tasmania) to cut for an avid prospector. The two I will begin with are quite different in nature. A smaller stone with good clarity and light colour, and a larger, quite dark blue stone, with distinct growth bands visible.

Gee, Tasmanian sapphires when well-coloured can match it with the very best.

Frome River (NE Tas) sapphire, 2.2ct
5.5ct sapphire: dopped and ready

This large stone, dopped above, would benefit from being cut as shallow as possible to help lighten it, whilst still considering the critical angle of 34.45°. I think the Jeff Graham Quickie 2 may be a good choice @ 91.2% light return.

Quickie 2 cut

Ok – update, having started the pavilion, some cracks that were not visible before cutting, due to the darkness of the stone, are clearly apparent now. This is a typical example of the sorts of challenges that often present themselves during the cutting process.

This has lead to a rethink as to the best cut. The roundish Quickie would now yield unacceptably low, a more rectangular stone would be better so that I can cut the defects off without losing too much stone carat weight.

Obvious cracks and defects
This angle clearly reveals the growth lines

Changing to a rectangular cushion cut, the Tsunami-311 in fact.

Rectangular cushion cut – Tsunami 311
Looking better, still some more to cut off top-left
And better..
Good!

Time for some polishing

Pavilion polished and ready for transfer
Transfer in progress – epoxy on top, wax on bottom.
Crown underway
So far, so good
Table is in
Interesting stone – this cut is much harder than I thought it would be..
look at those bands!
Shiny as.
Pre-polish was tricky, but all done now, very pleased. Final polish next.

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NW Tasmanian (Table Cape region) sapphire and zircons

NW Tasmanian sapphire and zircons

Above are some largish well-formed examples of Tasmanian stones sent to me recently for cutting. The 4.9 ct  sapphire pictured above is a nice example of the dogs-tooth shaped crystal habit.

I have been examining the sapphire above whilst trying to determine the best orientation, taking into account inclusions/cracks etc.

Dopped and ready

I think the orientation above will give the cleanest stone with the highest yield – so many factors involved in creating the best final product. A rectangular cushion cut, the Tsunami 311, as per this post is the selection.

Pavilion underway. If you look carefully you will see a small crack on the RHS near the girdle area
Crack a bit more clearly visible. It should cut out OK.
Another view, crack is original with some iron oxide present.
Fixed and continuing with pav. Yield down a little.
Prepolish going in, nice colour coming through now.

Final polish on pavilion (I know I’m really slow, lol)

final polish #60K diamond
Transfer for crown – purty colour!
epoxy on top (with filler powder added to reduce runniness and increase strength)

On to the crown..

OK, just cut the two A facets on the crown
B crown facets
B crown facets
H facet in, about to do I facets
Table facet in
All facets done, time for pre-polish
Pre-polish going well, you can clearly see the unpolished frosted H and I facets adjacent to the table standing out
H and I facets left.
Pre-polish complete

Final polish ahead.

Most facets done, ready to put the final polish on the table
Table adapter on
Shiny, shiny, bad times behind me!
This is one sweet Tassie stone
Stunning.
This stone turned out real good..

Yield a little lower than I would have hoped at the start, however this is a really clean stone as a result, great colour (and great cut too I must say!)

 

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