January 24 Through February 4—TUCSON, ARIZONA: Annual show
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Thu Mar 28, 2024 10:45 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 8 posts ] 
Author Message
 Post subject: A Concave Star?
PostPosted: Wed Aug 25, 2021 6:55 pm 
Offline
Platinum Member
User avatar

Joined: Fri Feb 24, 2006 1:20 am
Posts: 2756
Location: Southern California, U.S.A.
I reallly AM asking for a friend: if a synthetic boule of star corundum is cut concavely, will it star? The notion seems to tickle a memory buried deep in my brain that says "yes." It seems logical to me that if the silk is distributed evenly through the boule a star should be evident both convexly and concavely if the boule is oriented properly. Opinions? Thoughts? Thanks.

_________________
Rick Martin

www.artcutgems.com


Top
 Profile  
Reply with quote  
 Post subject: Re: A Concave Star?
PostPosted: Wed Aug 25, 2021 7:00 pm 
Offline
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 4015
Location: North Carolina
Should do, yeah. It works with star rose quartz anyway.

_________________
Rough and cut classic and exotic synthetic gems:https://store.turtleshoard.com


Top
 Profile  
Reply with quote  
 Post subject: Re: A Concave Star?
PostPosted: Thu Aug 26, 2021 9:27 pm 
Offline
Valued Contributor

Joined: Fri Jun 25, 2010 12:04 am
Posts: 257
Location: Idaho
Stewarts Gem Shop in Boise, Idaho have a 6-ray star garnet cut that way, a polished concave hemisphere cut in to a piece of Emerald Creek material.

_________________
Lapidarist by Passion
Goldsmith by Necessity

Facetron x2
Polymetrics OMF
GemCad/GemRay/Gem Cut Studio
Matrix 9/Rhino 5, 6, 7
REVO A (still hanging on...)
B9 Creator Core 5 Series XL
Indutherm MC-15


Top
 Profile  
Reply with quote  
 Post subject: Re: A Concave Star?
PostPosted: Thu Aug 26, 2021 9:38 pm 
Offline
Gold Member
User avatar

Joined: Tue Apr 05, 2016 7:58 pm
Posts: 1424
Location: San Marcos, CA
ROM wrote:
I reallly AM asking for a friend: if a synthetic boule of star corundum is cut concavely, will it star? The notion seems to tickle a memory buried deep in my brain that says "yes." It seems logical to me that if the silk is distributed evenly through the boule a star should be evident both convexly and concavely if the boule is oriented properly. Opinions? Thoughts? Thanks.

What do you mean exactly cut concavely? In the sense of a cabochon or a concave faceted stone or other?

_________________
The Gem Garden
San Marcos, CA


Top
 Profile  
Reply with quote  
 Post subject: Re: A Concave Star?
PostPosted: Sat Aug 28, 2021 3:26 pm 
Offline
Valued Contributor

Joined: Fri Jun 25, 2010 12:04 am
Posts: 257
Location: Idaho
Here is a rendering of a "concave star", a reverse dome cut in to a piece as I mentioned above in star garnet.


Attachments:
Concave Star.JPG
Concave Star.JPG [ 23.28 KiB | Viewed 2202 times ]

_________________
Lapidarist by Passion
Goldsmith by Necessity

Facetron x2
Polymetrics OMF
GemCad/GemRay/Gem Cut Studio
Matrix 9/Rhino 5, 6, 7
REVO A (still hanging on...)
B9 Creator Core 5 Series XL
Indutherm MC-15
Top
 Profile  
Reply with quote  
 Post subject: Re: A Concave Star?
PostPosted: Sat Aug 28, 2021 4:14 pm 
Offline
Gold Member
User avatar

Joined: Tue Apr 05, 2016 7:58 pm
Posts: 1424
Location: San Marcos, CA
As a 3d Rendering I get that, is that what you mentioned at the Idaho shop?
So in theory lets take, say a 12mm Round high dome cabochon. It has a star and all is orientated correctly, we take 10mm Round nose set of diamond bits and create the polished concave as your rendering, we will or maybe will have a star of similarity as the convex cab had?

_________________
The Gem Garden
San Marcos, CA


Top
 Profile  
Reply with quote  
 Post subject: Re: A Concave Star?
PostPosted: Sun Aug 29, 2021 1:33 am 
Offline
Valued Contributor

Joined: Fri Jun 25, 2010 12:04 am
Posts: 257
Location: Idaho
Here you go. Don't need sleep anyway...

Brazilian 4-ray star garnet, had polished the top top locate/orient the star but never finished cutting this piece...

First is a top picture of the convex polished "cab" and star.

Second is a picture of the bottom of the piece. I cut two 4 mm cups in to the surface with a diamond ball burr, then gave it a quick (sort of) pre-polish with 3,000 diamond on brass. Then a little WDE 40 to give it a better shine. It is just a quick and crude experiment/proof of concept, after all!

Pictures taken with my iphone, using its flash to show the star.


Attachments:
File comment: Quicky orientation surface on a piece of Brazilian 4-ray star garnet.
Braz 4-Ray Star top (460x600).jpg
Braz 4-Ray Star top (460x600).jpg [ 226.31 KiB | Viewed 2178 times ]
File comment: Two roughly polished concave surfaces showing 4-ray stars, in back of piece.
Braz 4-Ray Star Conc 1 (464x600).jpg
Braz 4-Ray Star Conc 1 (464x600).jpg [ 242.82 KiB | Viewed 2178 times ]

_________________
Lapidarist by Passion
Goldsmith by Necessity

Facetron x2
Polymetrics OMF
GemCad/GemRay/Gem Cut Studio
Matrix 9/Rhino 5, 6, 7
REVO A (still hanging on...)
B9 Creator Core 5 Series XL
Indutherm MC-15
Top
 Profile  
Reply with quote  
 Post subject: Re: A Concave Star?
PostPosted: Sun Aug 29, 2021 2:01 am 
Offline
Gold Member
User avatar

Joined: Tue Apr 05, 2016 7:58 pm
Posts: 1424
Location: San Marcos, CA
There you have it, concept challenge accepted and proven.
Thanks, get some zzz's now.

_________________
The Gem Garden
San Marcos, CA


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 26 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock