Jump to content

Advice Please? Diamond Value - Fancy Coloured Diamonds From Indonesian Borneo


Recommended Posts

Hi there, 


From a friend I received some coloured stones from Indonesian Borneo. I expected sapphires, but on the advice of a friend I tested them with a diamond tester, and it seems virtually all of them are diamonds. They're small, perhaps 3-4 mm on average, but I am attracted by the colors. 


This friend is soon going back to the village from where she got these diamonds, and I would like to ask her to get me more.


Any chance you can give me some advice on the potential worth of these diamonds? What would be a reasonable price to purchase them? What would be a reasonable price to sell them set in jewelry?


I'm attaching a picture. Sorry, I don't have a micro lens, so this picture does not do justice. It just shows the color a bit.


Thank you :)

Link to comment
Share on other sites

Hum. A "diamond tester" is hardly conclusive evidence that what you have is a diamond; there are diamonds in Borneo, so it could be, though they come from well identified areas. In any case, regardless of whether they are diamonds, sapphires, garnets or anything else, "value" would depend on several factors:


1) Colour

2) Quality of the rough (transparency, inclusions)

3) Facetability/shape and expected yield

4) Size

5) Market in which you intend to sell (as a "one off" loose rough, set in jewellery - rough or cut, on "industrial" scale)


To give you an idea of price ranges, a large rough unfacetable brown crystal, well formed and thus interesting from a mineral collection point of view could get a fifty to a hundred US$/carat; facetable small brown rough (cut stones of 0.10-0.20 ct) is about the same price, but for smaller pieces it is far less; small facetable pink rough from Argyle is twenty times as much or more. This all assumes you can get cutters to be interested...


BTW - the picture did not appear, but it doesn't matter: there is not much anyone can tell without seeing the pieces (and being an expert in the market of rough diamonds, which I'm far from being!)

  • Like 1
Link to comment
Share on other sites

Thank you Davide! I reckon the pieces aren't much larger than 0.1 to 0.2 carat each, and of most, the shape isn't ideal for cutting. They were found by villagers when they were mining for gold, and diamonds are found in the area.


I tend to sell them as one off loose diamonds set in jewellery.


Here is a link to the picture http://instagram.com/p/qZI1rUhIi2 largest is around 5mm in width, many are rather flat shaped. 

Link to comment
Share on other sites

For ease of following the thread, here is the image (meeuwie - if you don't want it displayed here, let me know; it's just linked, so if you take it down from Instagram it will go here too)




FWIW, looking at the image, these seem to me to be mostly corundum (i.e. sapphire/ruby); they are too rounded/broken to be alluvial diamonds, and the shapes are "wrong" even for macles (flat diamonds). Also, the presence of pink, blue and violet is indicative of corundum - as far as I know, although violet diamonds do exist, they are extremely rare and not found together with pinks.


Here is a photo of a few roughs found in Borneo:




Also, the info I have on Borneo diamonds indicates that though some pinks and blues have been found, they represent less than 1% of stones, and the chance of finding such a lot of 40-50 stones would be very low indeed.


Thermal conductivity-based diamond testers are not reliable (IMHO) on small irregular stones, but a definitive test using density/specific weight is quite easy to perform.


In either case, given size, shape and appearance, I don't think the price would be "high", however "high" depends on whether these really are pink and blue diamonds or - as I suspect - pink and blue sapphires. "Not high" in the case of diamonds could be several hundred $/carat, but no more than a few tens for corundum.


Sorry for sitting on the fence... but it's the best I can do!

Edited by davidelevi
Link to comment
Share on other sites

As someone who is experienced in minerals, I think Davidelevi is correct in guessing the stones are most likely corundum (sapphires).  They could also be spinels which can be found in the same colors but I don't think are commonly found with such a range in colors from one single location like corundum might be. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...