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 Tue Mar 19, 2024 3:29 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 12 posts ] 
Author Message
 Post subject: The origin of carbonado
PostPosted: Sun Jan 24, 2016 5:10 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Thu Feb 22, 2007 10:23 am
Posts: 923
Location: NYC
good article about the origin of Carbonado here:

http://www.geologyin.com/2015/10/what-a ... -they.html

_________________
Farshid Roshanravan


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Sun Jan 24, 2016 5:26 pm 
Offline
Gold Member

Joined: Mon May 26, 2014 9:42 pm
Posts: 1031
A strange article. In the first paragraph it says it is found in Central Africa, Brazil, Venezuela, Eastern Australia, and possibly Russia.
In the last paragraph it says it is only found in Brazil and the Central African Republic.

" Brazil and the Central African Republic, the only two known locations of carbonado deposits."


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Sun Jan 24, 2016 6:35 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21600
Location: San Francisco
As you may recall, a new member started a similar thread and after a week or so deleted all his/her content and replaced every post with "0".

That thread was deleted (as it lacked content , cough cough). Please carry on here for the discussion.


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Sun Jan 24, 2016 11:48 pm 
Offline
Gold Member

Joined: Mon May 26, 2014 9:42 pm
Posts: 1031
Here is another article, from the New York Times:

http://www.nytimes.com/1996/09/17/scien ... wanted=all


Top
 Profile  
Reply with quote  
 Post subject: Possible Carbonado Black Diamond?
PostPosted: Sun Aug 21, 2016 2:55 am 
Offline
New to the Forum or The Quiet Type

Joined: Tue Oct 28, 2014 11:22 am
Posts: 5
My specimen was purchased online as a Chinese Scholar Rock/Japanese Suiseki several years ago by my brother as a gift to our mother who did not fancy it. He gave it to me. Eventually I began searching online for similar specimens because it was so unusual in character. I learned about Carbonados and meteorites, and researched all I could about them.

A description of my specimen: The very hefty, rather shiny pure black rock is extremely coherent, and does not attract to a magnet or a paper clip. When I strike a ring on my finger off the rock, it clangs like a bell, as if there are hollow voids inside. It has anomalous large wave-like protrusions. Throughout major portions of the rock, there are filaments of intersecting shock veins (like wrinkled skin) and twisting sparkling necklaces of what appear to be micro-diamond material cutting through and merging into the black matrix surface. In some areas the rock has pores, whereas in other areas there are protrusions and dimples. There are locations of very smooth surface character. On the somewhat flat bottom are orange patches fused to the black surface. Outdoors in mid-day sunlight, color tones of pink and purple glint off the black surface at certain angles. I know that carbonados are found almost exclusively in Brazil and West Africa, however i know of famous Black Orlov which was found in India... I believe that this rock is a Carbonado.

The Rock weighs 3,902 grams or - should I dare say - 19,510 carats! Please advise me where I can get verification, perhaps in New York. I would hesitate to use GIA, because I had unpleasant previous experience with them.

I have many photos of the rock posted in my Flickr album, which I admit sheepishly is titled "Carbonado Black Diamond Meteorite". There are images of another rock of mine that I also believe is a carbonado. I also posted some other images of known carbonados I found online including Sergio... The best way to view the images in the album is right-click the link below and open in new browser, then you can view as a slide show or each image individually. I recommend that you hit f11 key for full screen viewing. Hit f11 key again to escape full screen.

Thank You All!

Here is the link:
https://www.flickr.com/photos/70834779@N05/albums/72157668730287444


Attachments:
IMG_1700 02 small size.JPG
IMG_1700 02 small size.JPG [ 51.8 KiB | Viewed 2247 times ]
IMG_1708 01 small size.JPG
IMG_1708 01 small size.JPG [ 68.36 KiB | Viewed 2247 times ]
Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Sun Aug 21, 2016 4:30 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21600
Location: San Francisco
I moved this post to a former thread on carbonado.


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Sun Aug 21, 2016 5:16 pm 
Offline
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 4015
Location: North Carolina
My guess would be some sort of hematite-rich rock. Try scratching an inconspicuous edge across white ceramic (like the bottom of a coffee mug if you have one you don't mind testing with) and see what color the scrape is.

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


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Mon Aug 22, 2016 7:06 am 
Offline
New to the Forum or The Quiet Type

Joined: Tue Oct 28, 2014 11:22 am
Posts: 5
Hi Stephen, thanks for your reply. Thank you Barbara for re-posting on this thread...

Hematite is ferric oxide which is the main source of iron ore. its name is derived from the Greek word for “blood,” because of its red color (as in hemoglobin). I scratched my rock in various places on the back unglazed side of a piece of ceramic tile. It scraped ceramic particles right off the tile, and left no streaks, which would have been red were it hematite. correct?

Referring to the link posted above about carbonados on GeologyIn.com, there is another link at the end of that article titled "The Largest black diamond ever found" posted on September 25, 2015

http://www.geologyin.com/2015/09/the-largest-black-diamond-ever-found.html

They identify the rock in the image on that page as being Sergio from Minas Gerais in Brazil, and which was found at the turn of the 20th century over 120 years ago or so. The rock in that photo is not Sergio. Sergio was shipped to New York shortly after its discovery. it was then ground up and used in drilling iron ore in Montana. Here is a photo of Sergio from a 1905 Popular Science Magazine article about the rock:
Attachment:
File comment: Sergio Carbonado weighed 633.4 grams or 3,167 carats
Sergio carbonado - img resize.jpg
Sergio carbonado - img resize.jpg [ 126.51 KiB | Viewed 2205 times ]


The image of the rock wrongly Id'd as Sergio is actually 1 of 5 photos uploaded by a user on London's Natural History Museum NaturePlus Discussions forum in a thread titled "Is this a Carbonado Black Diamond?" This the link:
http://www.nhm.ac.uk/natureplus/thread/9013?fromGateway=true

I also posted my own thread on that site:
http://www.nhm.ac.uk/natureplus/message/86616#86616

PLEASE GO TO MY flickr PHOTO ALBUM TO SEE DETAILED HI-RES IMAGES OF MY ROCK!!
https://www.flickr.com/photos/70834779@N05/albums/72157668730287444


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Mon Aug 22, 2016 2:07 pm 
Offline
Moderator: Lapidary Diamonds
User avatar

Joined: Mon Aug 20, 2012 11:32 pm
Posts: 1747
Location: Florida, United States
Also, check to see if this specimen is magnetic with a small rare earth magnet.

_________________
http://adamasfacet.com


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Mon Aug 22, 2016 3:12 pm 
Offline
Gold Member
User avatar

Joined: Fri Oct 19, 2007 5:04 pm
Posts: 1642
Location: Walnut Creek, CA
That's very likely a black limestone with calcite veins.
The composition+texture of the limestone gives it a shiny finish when tumbled and/or weathered, while the white veins made out of calcite weather at a faster rate, as observed in the sample. With quartz veinlets it is common to observe the opposite pattern. :)

I've seen a few of them as suiseki...

_________________
https://www.instagram.com/marcovoltolinifaceting/


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Mon Aug 22, 2016 4:53 pm 
Offline
Gold Member
User avatar

Joined: Fri Oct 19, 2007 5:04 pm
Posts: 1642
Location: Walnut Creek, CA
I quickly checked, and apparently they can also do a "man-made" ;) weathering on these stones. And they do it pretty well, I've to say!
Well, I've learned something new...

Btw, this site also says similar stones are made out of limestone:
http://ibonsaiclub.forumotion.com/t1572 ... ngxi-china

_________________
https://www.instagram.com/marcovoltolinifaceting/


Top
 Profile  
Reply with quote  
 Post subject: Re: The origin of carbonado
PostPosted: Sun Oct 09, 2016 5:36 pm 
Offline
New to the Forum or The Quiet Type

Joined: Tue Oct 28, 2014 11:22 am
Posts: 5
Hello All! Here are some closeup photos of my specimen showing porosity, luminescent purple and pink hues, and a string of tiny crystals embedded in the rock. Your opinions are most appreciated. Thanks again!

Attachment:
IMG_2164 02 01 small.JPG
IMG_2164 02 01 small.JPG [ 46.58 KiB | Viewed 2101 times ]
Attachment:
IMG_2157 03 small.JPG
IMG_2157 03 small.JPG [ 44.52 KiB | Viewed 2101 times ]
Attachment:
IMG_1657 04 small.JPG
IMG_1657 04 small.JPG [ 50.48 KiB | Viewed 2101 times ]


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 2 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