Indonesia does produce some amazing chalcedonies of many sorts. That said, that color does not look at all natural to me.
I have been cutting a bit of carnelian recently. I bought a big bag of rough carnelian online, but so far about 95% have actually been pale yellow, maybe with a wisp or stain of orange inside. I may try heating some just to see what it will do. That said, a few had a nice natural red-orange color. Interestingly, one that I slabbed up ended up having a mixture of banded zones and zones with phantom botryoidal zoning inside. I don't think it's just a matter of how banding is oriented either (edit: it is actually, I just cut across the banding--it is much better looking imo)? It is certainly an interesting effect, and gives it more of a "gel chalcedony" look than an "agate that happens to be red-orange" look. Still nothing like the ancients were carving but maybe heating will yield similar stones.
Aside from top grade purple ones, Indonesia also has fine red natural & untreated Chalcedony...
The pictures posted are not examples of that. Chalcedony does not naturally occur in that color.
Maybe it does but isn't discovered yet (or it's already found like those red beauties from the underrated Pacitan, Indonesia) 'cos most people from the trade are too focus on the chalcedony/carnelian from other locations (africa, brazil etc.) just sayin'
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Well, think this through. If it is pictured above, it has been discovered. There is no mineralogical, gemological or empirical verification of the existence of this unique naturally occurring cherry red chalcedony.
A lot of attention is being paid to Indonesia right now thanks to the great chalcedonies of various sorts. I've seen a number of examples of the fine carnelian from there but none had color near to that. Carnelian is colored by iron oxides/hydroxides and because of that there's a somewhat limited range of colors it can show. Something with this sort of pinkish magenta-red would need a completely different colorant which has never been seen before, something that would definitely attract a lot of gemological interest (see the recent article on 'aquaprase' which is just a hybrid of two well-known colorants).
Well, think this through. If it is pictured above, it has been discovered. There is no mineralogical, gemological or empirical verification of the existence of this unique naturally occurring cherry red chalcedony.
There's one but it's written in indonesian (actually most of the references online are in bahasa language I had to use google translate to be able to read/understand it hehe)
I don't know why the photo looks pinkish red (but its main color is red nonetheless) probable due to outdoor lighting... Try searching for "Red Baron Pacitan Blood Carnelian" it's pure dark red with very very little brown/orange tinge.
Aquaprase was just discovered & accepted early this year by GIA (but prior to that, there's also no mineralogical, gemological or empirical verification of the existence of this aquagreen gem except for gem silica & chrysoprase) I guess the same thing can apply for indonesian red carnelian. It truly exist in nature...
I know that heat treatment of carnelian is 1000s of years old and was used on ancient stones as well. However, I'm left with the questions: - where and how did the ancients get this beautiful deep coloured carnelian? - why can't I find this beautiful variety anywhere today? and - Is there actually something like "natural carnelian", given that the ancients used heat treatment too?
I think Ancients got it by digging/fossicking through riverbeds and hills? Hehe not so sure
I think it's hard to obtain today because most carnelians are treated/enhanced or the color/luster isn't appealing and the gem market only offers materials (of this type) mostly from western countries (South America), Africa and India.
I myself was losing hope of finding a nice carnelian until one day, while searching for a nice namibian blue chalcedony for a ring project, I came across this Indonesian local who mentioned about chalcedony from his country. I was skeptic at first because I've never heard about it. I only knew about their country and that their black opals are untreated and cheaper than black opals found in Australia hehe... And the rest was history.
Anyway, back to the topic... Here's what my Indonesian middleman/vendor explained to me about the Chalcedony (esp. Red Carnelian) found in their country. -- Carnelian can be orange, brownish red, reddish orange, yellow orange, or the rarest/appealing red/blood red colors.
There are 3 known types of Red Chalcedony in Indonesia:
* Red Reflesia Cempaka - from Bengkulu Province, Indonesia
these are popular and from the name itself, its color resembles the giant flower in the world - Red with slight hint of orange -- more like a deep red-orange color and good translucency esp. under a strong light source.
* Red Baron - from Pacitan, Indonesia
these are high gem grade - it's highly translucent and some fine materials (be it a yellow, orange, red or white chalcedony) display chatoyancy/cat's eye effect and beautiful adularescence -- like a scattered billowing light. It's truly a coveted carnelian and the most expensive ones are the vibrant red and deep tomato red-orange colors.
* Red Cempaka Aceh Syrup / Cempaka Merah Sirup Aceh - from Aceh province, Indonesia
these carnelians are not as famous as the first two mentioned. It has good translucency but not as gemmy as the red baron and the red raflesia. it doesn't display adularescence but its color is truly beautiful -- Blood red / Crimson red in normal light (and a shocking red under a strong light source and in outdoor) --- this material also has minimal orange tinge. Most are red red red / pinkish red, deep dark red, merlot red, and the famously called by the locals: Fanta Red Cempaka Aceh and Red Syrup Cempaka Aceh.
And all those 3 chalcedony materials have natural, untreated colors that's why they're highly sought after by gem enthusiasts and collectors in Indonesia.
I'm sure a lot of us have seen dyed chalcedony pebbles that look just like this, sold to be placed in bowls for display. I have seen such exactly that color, and a lot of other colors as well. My knee jerk reaction in seeing that picture is the same as many others - yup, dyed.
I only knew about their country and that their black opals are untreated
What makes you think indonesian black opal is untreated? Treatment is pretty universal in them from what I've seen, particularly oiling. I picked one up online--lovely black base, sparks of fire, overall similar appearance to smoked ethiopian opal. A few hours in acetone and it was... just wood. Brown, porous, no-hint-of-color, no doubt somewhat petrified wood.
I only knew about their country and that their black opals are untreated
What makes you think indonesian black opal is untreated? Treatment is pretty universal in them from what I've seen, particularly oiling. I picked one up online--lovely black base, sparks of fire, overall similar appearance to smoked ethiopian opal. A few hours in acetone and it was... just wood. Brown, porous, no-hint-of-color, no doubt somewhat petrified wood.
I stand corrected, yes some indonesian black opals are treated (mostly with baby oil) but there are also some that are untreated. I'm sorry to hear about your petrified wood story that was sold to you as opal. I've read about that practice and seen sample videos of how they do it (foil, sand, candle/lighter etc.) were you not suspicious when you saw the play of colour pattern? Did you not ask for some videos or even macro shots (from diff. angle) of that opal? 'cos I think you can somehow discern the real one from petrified wood esp. if the color pattern is just like sprinkles of glitters. Not sure if I can post (as reference) the youtube link of the indonesian black opal I bought from there.
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