CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Fri Nov 22, 2019 10:42 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 115 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8  Next
Author Message
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Sun Dec 12, 2010 2:20 pm 
Offline
Platinum Member
User avatar

Joined: Fri Feb 24, 2006 1:20 am
Posts: 2742
Location: Southern California, U.S.A.
Thanks for all the nice comments everyone!

Doug, Bruneau and the other porcelain jaspers do indeed take a great polish. They're extremely dense and hard. But I think the luster of darker-toned stones may be more apparent in images. The polish on light-toned stones of different types can be as good but isn't as reflective, or at least it seems so to me. Of coiurse it also depends on the luster value of the material in question: vitreous, greasy, etc.

I think it also depends on the quality of light at the time the images are made. I use natural light most often to photograph cabochons and there are notable luster differences between shots made when skies are sunny, overcast, foggy etc.

_________________
Rick Martin

www.artcutgems.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Sun Dec 12, 2010 3:23 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Fri Sep 08, 2006 7:03 pm
Posts: 606
Location: Sweden
Opalized wood can be really lifelike, here is a specimen from Hungary.

Image

_________________
If it sounds good, then say it again!


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Sun Dec 12, 2010 3:53 pm 
Offline
Platinum Member
User avatar

Joined: Fri Feb 24, 2006 1:20 am
Posts: 2742
Location: Southern California, U.S.A.
Great stone JK! Just for the record, the Washington Sycamore is also opalized.

_________________
Rick Martin

www.artcutgems.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Sun Dec 12, 2010 4:18 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Fri Sep 08, 2006 7:03 pm
Posts: 606
Location: Sweden
Thx, I bought it from an old emigrant from Hungary, although the find seems pretty recent. A couple of years later I saw whole tree stumps with roots of this material.

Continuing the cab run, I've always been fascinated by effect stones:

Image

Image

Image

Image

_________________
If it sounds good, then say it again!


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Mon Dec 13, 2010 3:10 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Tue Feb 03, 2009 12:19 pm
Posts: 914
Location: California, USA
Jung Kee, what is the last star stone?

Not as much and good as faceting, but I do cut cabochons.
Image
This is hawk’s eye, my practice piece for chatoyant stones. (Now I realized it looks like a roly-poly aka wood louse. :( )

I have seen a picture of a round cabochon that shows chatoyancy in a concentric pattern. I tried a couple of orientation to cut like that. For example, I oriented the fibers perpendicular to the cab bottom, but no success. Any cutting suggestion would be appreciated.

Image
Image
This is opal from Shewa, Ethiopia. One still picture does not do justice to an opal. So I post two. :mrgreen:

_________________
Best regards,
Mitch

I am a slave to cutting a stone completely free of chips and very much enjoying it.


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Mon Dec 13, 2010 5:28 pm 
Offline
Platinum Member
User avatar

Joined: Fri Feb 24, 2006 1:20 am
Posts: 2742
Location: Southern California, U.S.A.
mhuynh wrote:
Jung Kee, what is the last star stone?

The image makes the ID pretty obvious. Study the growth structure.
Quote:
This is hawk’s eye, my practice piece for chatoyant stones. (Now I realized it looks like a roly-poly aka wood louse.

Tiger's-eye and Hawk's-eye show chatoyancy better when cut as fairly shallow stones, with the base aligned to the "grain" of the fibers. Because the patterns are usually quite large the effect is usually more dramatic in larger cabochons.
Quote:
I have seen a picture of a round cabochon that shows chatoyancy in a concentric pattern.

Do you mean concentric like a bull's-eye? Can you post an image? I've cut a lot of that material and have never seen or heard of such a thing. Cat's-eye effects are possible from very straight-grained rough.

_________________
Rick Martin

www.artcutgems.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Mon Dec 13, 2010 6:41 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Tue Feb 03, 2009 12:19 pm
Posts: 914
Location: California, USA
ROM wrote:
The image makes the ID pretty obvious. Study the growth structure..

I thought it’s corundum. But just wanted to ask.

ROM wrote:
Do you mean concentric like a bull's-eye? Can you post an image? I've cut a lot of that material and have never seen or heard of such a thing. Cat's-eye effects are possible from very straight-grained rough.

It wasn’t a photograph but a drawing appeared on page 19 in Advanced Cabochon Cutting by Jack R. Cox.

The text says “Another novel effect requires a good piece of close, straight-grained tigereye. Saw a thick slab parallel to the plane of the eyes (perpendicular to the fibers). Cut a high crowned, round cabochon from the slab to produce a bull’s-eye effect of alternating light and dark bands. This cut requires good material and skill.”

I thought I did as described. It wasn’t alternating bands, but a golden cabochon with a chocolate brown round center area. I guess the material and/or skill wasn’t good enough.

_________________
Best regards,
Mitch

I am a slave to cutting a stone completely free of chips and very much enjoying it.


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Mon Dec 13, 2010 6:49 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Fri Sep 08, 2006 7:03 pm
Posts: 606
Location: Sweden
Indeed it is a star corundum. Tried to photgraph a star ruby, but it didn't turn out good so I too this instead, while nothing special in colour it has a very good asterism.

I tried that kind of cut too once, but most of the stone turned up darkish, so it really needs suitable material and very careful orientation to become nice.

Attached is an agate that looks like an eye. Origin unknown.

Image

_________________
If it sounds good, then say it again!


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Mon Dec 13, 2010 7:26 pm 
Offline
Platinum Member
User avatar

Joined: Fri Feb 24, 2006 1:20 am
Posts: 2742
Location: Southern California, U.S.A.
Let the staring contest begin! The eyes have it!
Attachment:
Picture 452.jpg
Picture 452.jpg [ 18.25 KiB | Viewed 1375 times ]
Attachment:
DCab 81.JPG
DCab 81.JPG [ 34.28 KiB | Viewed 1375 times ]

_________________
Rick Martin

www.artcutgems.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Tue Dec 14, 2010 12:44 am 
Offline
Valued Contributor
User avatar

Joined: Fri Nov 12, 2010 11:37 pm
Posts: 237
Location: Warsaw, IN
JungKee, ROM, I'm just not sure how people would react to a piece of jewelery that appears to be staring at them. However it must certainly be fun to see all the double takes one would get.
Mitch, I may be reading this wrong, and truthfully I have no hands-on experience cutting cabs, however, the description of how to cut the bulls-eye seems to be relying on the alternating colors of the stria in the stone rather the crystal arrangement that is required for asterism or chatoyancy. When attempting it, first have a stone with very clear banding, when dopping up make sure that only one color is showing, say the darker brown of a tiger eye on the surface parallel to the dop, from the side of the stone (ie, perpendicular to the dop) the seperate layers of color will be evident as stripes. Hope that helps in some small way next time you take a crack at this effect.

_________________
- Jonathan R. Enck

The glass is completely full, however the ratio of liquid to air may not be to your personal preference.


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Tue Dec 14, 2010 12:54 am 
Offline
Gemology Online Übergoddess
User avatar

Joined: Mon Oct 06, 2008 6:13 pm
Posts: 5018
Location: Australia
That first one of ROM's would be fun...definitely calls for being an owl or Panda. 8)

_________________
Keep em comin!!!

Most of the fire on the wall has been put out :)


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Tue Dec 14, 2010 1:22 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 19909
Location: San Francisco
ROM, is there an example of :?: anything you don't have in your collection?
WOW!


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Tue Dec 14, 2010 2:47 am 
Offline
Gemology Online Veteran
User avatar

Joined: Fri Oct 30, 2009 9:19 pm
Posts: 591
Location: Las Vegas, NV
Barbra Voltaire wrote:
ROM, is there an example of :?: anything you don't have in your collection?
WOW!


No kidding...

:wink:

_________________
-Ryan Quantz, A.J.P. (GIA)
-Lapidary and Jewelry Artist
http://www.etsy.com/shop/RyanQuantzStudios


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Tue Dec 14, 2010 8:27 am 
Offline
Established Member

Joined: Tue Dec 14, 2010 2:10 am
Posts: 44
The rough amber was send to me by an Indonesian guy, which his father mined this unusual fossil resin material from West Java Island in Indonesia. I test them with acetone and hot pin test, all pass the test. It was very hard type of amber, I think slightly harder than ordinary Baltic amber. In raw they covered with a few mm of hard rocks and some lignite matrix. All material was photograph under sunlight.

Image
Deep blue color with translucent red
Image
Blue color with sub-transparent yellow.


Top
 Profile  
Reply with quote  
 Post subject: Re: Select Stones, Cabochon Special Edition
PostPosted: Tue Dec 14, 2010 12:18 pm 
Offline
Platinum Member
User avatar

Joined: Fri Feb 24, 2006 1:20 am
Posts: 2742
Location: Southern California, U.S.A.
Barbra Voltaire wrote:
ROM, is there an example of :?: anything you don't have in your collection?
WOW!

Nice comment, and thanks. But there are many others who have much greater selections. Still it's fun showing off some of my pet rocks and seeing those of other Forum members.

I greatly enjoy all aspects of the gem world: faceting, cab cutting, carving and minerals. All are expressions of my fascination with the earth sciences and the way the Earth is put together.

_________________
Rick Martin

www.artcutgems.com


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 115 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 3 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