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 5:50 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 25 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Negative crystals ???
PostPosted: Tue Jul 03, 2012 5:51 pm 
Offline
Valued Contributor
User avatar

Joined: Sat Oct 13, 2007 9:03 am
Posts: 109
Location: Italy
Negative crystals with tension halos into heat treated sapphire.
Image

Bye bye from Italy!

_________________
Paolo Cerruti G.G. (GIA)

"When the winds of change blow,
some people build walls and others build windmills"

www.paolocerruti.it


Last edited by Paolo Cerruti on Fri Jul 06, 2012 3:00 am, edited 1 time in total.

Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Tue Jul 03, 2012 7:01 pm 
Offline
Moderator
User avatar

Joined: Thu Dec 13, 2007 3:42 pm
Posts: 4091
Location: the Netherlands
=D>


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Tue Jul 03, 2012 8:12 pm 
Offline
Gemology Online Übergod
User avatar

Joined: Tue Aug 01, 2006 3:24 am
Posts: 4997
Location: McDonough GA
Blue paramecium? :)

_________________
http://www.selectgem.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Tue Jul 03, 2012 10:14 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
Awesome shot.
What else do you know about the sapphire?


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Wed Jul 04, 2012 5:55 am 
Offline
Site Admin
User avatar

Joined: Fri May 12, 2006 11:24 am
Posts: 7523
Location: Rome, Italy
bellissima Paolo, complimenti!!! =D> =D> =D> =D> =D> =D> =D>
ciao
albé

_________________
GemmoRaman-532 - GemmoFTIR - GemmoSphere - EXA


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Wed Jul 04, 2012 8:40 am 
Offline
Gemology Online Veteran
User avatar

Joined: Sun Oct 04, 2009 11:18 am
Posts: 595
Location: Madrid, Spain
Nice shot! =D>
But it looks more like crystalline inclusions of other mineral, IMHO.
Negative crystals in fact are cavities, where the form of the cavity corresponds to the form of the host mineral crystals.
When you have a group of negative crystals, they can't be oriented in different directions like in the shot. Their outlines correspond to the crystal structure of the host mineral, so they should be oriented identically.

Like, for example, this group in quartz:
Image
Photo from: http://www.sidcuplapminsoc.org.uk/Inclu ... vening.htm

_________________
http://gem-sphalerite.com
http://gems-inclusions.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Wed Jul 04, 2012 2:40 pm 
Offline
Site Admin

Joined: Thu Jan 05, 2006 4:27 pm
Posts: 1750
Wow two of the nicest pics I've seen for a while. I agree with Egor about the orientaion of negative crystals though

Great photography guys. How many shots did you stack to get this level of clarity?


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Wed Jul 04, 2012 9:51 pm 
Offline
Valued Contributor

Joined: Thu Jun 19, 2008 12:44 am
Posts: 113
Location: Illinois
Would the halos themselves be indicative of an expanding mineral inclusion instead of a negative crystal?

_________________
"The only people with whom you should try to get even are those who have helped you.”

― John E. Southard


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Thu Jul 05, 2012 4:21 am 
Offline
Valued Contributor
User avatar

Joined: Sat Oct 13, 2007 9:03 am
Posts: 109
Location: Italy
Thank you so much to everyone for have appreciated my shot...
I'm a beginner about the photomicrography, but I'm fascinated from this little world...
For Frank these are data of this photo:

Nikon D300 on trinocular Zeiss STEMI 2000C. exposure 1/8
Darkfield and fiber optical probe
12 different shots increasing the focus after I aligned and merge with Combined ZP software...


My first thought was that the inclusions were solid crystals because in the 3th book of photoatlas I found a very similar picture (prismatic apatite crystals)...But after this consideration I changed my opinion because with cross polarized filter I can't see the blink effect caused by birefringence of apatite crystals.
I don't know Barbra the origin of this stone, because it was inside of old parcel of my grandfather, so I think that these sapphires have almost 50 years old... It's a cabuchon cut, with a wk, ml tone and slgB hue...
I add a second photo of the same stone with a big gas bubble inside a cavity...
The photo was take perpendicular to the cabuchon, it's possible that these ipotetic negative crystal are be oriented 120° or 60°?

Image

_________________
Paolo Cerruti G.G. (GIA)

"When the winds of change blow,
some people build walls and others build windmills"

www.paolocerruti.it


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Thu Jul 05, 2012 6:50 am 
Offline
Gemology Online Veteran
User avatar

Joined: Sun Oct 04, 2009 11:18 am
Posts: 595
Location: Madrid, Spain
Frank wrote:
Great photography guys. How many shots did you stack to get this level of clarity?


The picture I posted is not mine, I posted the reference to the original site below.
I usually make 3-12 shots for stacking, depending on the size of the object of interest.

wavewalker wrote:
Would the halos themselves be indicative of an expanding mineral inclusion instead of a negative crystal?


Yes, it's the most common case. But halos on fluid inclusions are possible too, they can form in cases of natural decrepitation of inclusions due to overheating or decompression.

paolocerruti wrote:
I add a second photo of the same stone with a big gas bubble inside a cavity...
The photo was take perpendicular to the cabuchon, it's possible that these ipotetic negative crystal are be oriented 120° or 60°?


The cavity with the bubble looks quite different compared with the other inclusions. They don't seem to follow any specific pattern.

Additional comment: There is a particular case when "negative crystals" will not keep the symmetry of the host crystal at all. That will be the case of cavities formed after dissolved inclusions. Such inclusions don't fit to the strict definition of negative crystal but as a result we can have cavities with perfect crystal outlines inside of the host mineral, without any crystallographic correspondence. Quite a particular but not so uncommon case.
I have one sample with perfect rhombohedral inclusions in quartz, some of them with intact calcite crystals and some with yellow hydrocarbon filling with bubbles! Sometimes you can see tiny fissures reaching that cavities and responsible for later fluid circulation, but such fissures can be also completely healed by later quartz precipitation!
Other example of the same process is the well known Madagascan quartz with fluorite inclusions, where some inclusions are perfectly conserved (blue) and others are octahedron cavities (white). (this picture is mine! :D You can see some secondary fissures responsible for the dissolution of fluorite inclusions):

Image

_________________
http://gem-sphalerite.com
http://gems-inclusions.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Thu Jul 05, 2012 11:38 am 
Offline
Moderator
User avatar

Joined: Thu Dec 13, 2007 3:42 pm
Posts: 4091
Location: the Netherlands
Also, not every cavity (be it fluid or gas filled) has to be a negative crystal... If time has permitted it and the cavity is fluid filled a negative crystal may be the end result of 'healing' but usually there is a long road prior to that happening.

(general remark, I have no idea what those worms are)


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Thu Jul 05, 2012 7:28 pm 
Offline
Site Admin

Joined: Thu Jan 05, 2006 4:27 pm
Posts: 1750
For myself I just love these super real photographs...Kudos to those who produce them.


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Fri Jul 06, 2012 12:25 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
As a possibly related sidebar.
Dick Hughes recently said regarding what is considered a pardonable error:
Quote:
Seeing a crystal with a glassy tension halo in a sapphire, and thus believing it to be heat treated, but not locating a tiny CO2 bubble in a fingerprint (which would prove it is unheated).


Does anyone have a picture of such a CO2 bubble or additional information?


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals
PostPosted: Sun Jul 08, 2012 9:12 am 
Offline
Valued Contributor
User avatar

Joined: Sat Oct 13, 2007 9:03 am
Posts: 109
Location: Italy
Barbra Voltaire wrote:
Does anyone have a picture of such a CO2 bubble or additional information?


Some "guru" about corundum inclusions can help us? Also about my first post question, I would like to know other opinions about my photos and if this inclusions are cavities or crystals... Mr Richard Hughes...can you help us?

_________________
Paolo Cerruti G.G. (GIA)

"When the winds of change blow,
some people build walls and others build windmills"

www.paolocerruti.it


Top
 Profile  
Reply with quote  
 Post subject: Re: Negative crystals ???
PostPosted: Sun Jul 08, 2012 2:49 pm 
Offline
Platinum Member

Joined: Tue Jun 03, 2008 4:40 pm
Posts: 2667
Location: South Dakota
Great photos and information guys!!!!!

_________________
MrAmethystguy ~ Some jokes just fluorite over my head!


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 25 posts ]  Go to page 1, 2  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 8 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