Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on Mindat
What is a mineral?The most common minerals on earthMineral PhotographyThe Elements and their MineralsGeological TimeMineral Evolution
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
StatisticsThe ElementsMember ListBooks & MagazinesMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery
Indonesian purple chalcedony
Posted by Peter Slootweg
Peter Slootweg June 08, 2016 09:57AMLately i have seen a lot of specimens from Indonesia in the form of clusters composed of small spheres claiming to be chalcedony. I come's in purple, green, white and black hue's. I find it suspicious but beautiful material and there seems to be al lot of it. It is sold on the internet as grape agate/chalcedony. My question is if anybody can confirm this as natural, as all the specimens i have seen to date are without any matrix.
Keith Compton June 08, 2016 10:27AMHi Peter
They certainly look real to me, or at least the two that I have viewed up close.
Very nice under a scope too.
The "nodules" average around 1-4 mm in size. I would consider them too small to be artificially produced or carved like those Chinese "grapes" which are either quartz or fluorite and rounded with some form of sphere machine - basically all half spheres ground out of a solid mass. Many look very good admittedly but most have crude polishing around the base and they are obviously fake.
These from Indonesia look totally different.
Whether they are chalcedony or whether they could be called Amethyst - I am not sure but I think Chalcedony is correct
It would be good to have them analysed to ensure that they are not another mineral altogether. As more are appearing, I'm sure someone will do a definitive test. I see that some are described as Suiseki Chalcedony (those who grow Bonsai will be familiar with the term).
They are very nice.
I would certainly like to see more literature on the location.
Edited 1 time(s). Last edit at 06/08/2016 10:39AM by Keith Compton.
David Von Bargen June 08, 2016 12:35PMI saw one recently at a show and it was over a foot in size. These are definitely not carved. Most of the material is fibrous (radiating balls - therefore chalcedony), but there are some areas that have extremely small crystals growing on the surface so probably could be called amethyst.
Alfredo Petrov June 08, 2016 12:56PMI have the same observations as David. A few of the tiny crystals were twisted.... micro amethyst gwindels? :-S
And I wonder whether chalcedony can be colored by the same mechanism that colors amethyst? And then what would we call it?
Some parts of the deposit yield green balls rather than violet ones. Haven't had a chance to look at it under high power yet, so idk whether the green is intrinsic to the silica or due to an admixed substance like celadonite.
Some sellers at the Tokyo show had it labelled as being from Sulawesi, but none had visited the deposit. Eventually an exact locality will be found out, as usual, I suppose. Patience.....
Amir C. Akhavan June 08, 2016 02:07PMQuartzine (length-slow chalcedony) can grade into macrocrystalline quartz in botryoidal aggregates, as it does in amethyst specimen from Nyíri
The same probably happens here, too.
I could not think of anything that would generally preclude chalcedony (length-fast or lenght-slow) from possessing amethyst color centers. Of course, too many impurities could destabilize color centers and prevent their formation.
I think I've seen similar specimens from another locality, but can't remember from where.
You can heat a small piece to 300-350deg C and see what happens to the color. If you are very patient (several months), try to bleach one in the sun or UV.
Riccardo Modanesi June 08, 2016 02:46PMHi to everybody!
What you call "chalcedony" is truly amethyst. Amir is right: in Hungary some good specimens of this quartz, crystalized this way, are found. Therefore I fully agree with Alfredo. I think the specimen represented in the photo is real and natural.
Greetings from Italy by Riccardo.
Travis Hetsler June 09, 2016 06:16PMI have seen it called "Manakarra grape agate" and have a nice 4kg piece in my collection, purchased in Tuscon. Under magnification I see no signs of tool marks, etc indicating a man made carving. When broken open I see a radial structure, a nucleus, and the color is even throughout each orb with the nucleus just a tad darker than the rest.
Travis Hetsler June 11, 2016 03:48PMThere is also an "Indonesian Purple Chalcedony" or alternatively "West Java Purple Chalcedony", that forms deep purple veins as opposed to orbs, so I am sure the name "Agate" was used as a trade name to avoid confusing the two (which seems to have had the opposite effect lol). See link: http://www.indoagate.com/purple.html
Edited 2 time(s). Last edit at 06/11/2016 03:50PM by Travis Hetsler.
KEITH January 17, 2017 01:01AMI have recently acquired a kilo of small pieces of this material and after a thorough inspection I found several pieces that had little clear crystals on top of some of the spheres that when i examined with a jewelers loupe of 10x look like a perfect stilbite and some were clearly six sided quartz crystals with multiple termination on both ends. I know this is relatively new material and am still looking to see who has done some further mineralogical study on this material.
Christopher Jolicoeur March 24, 2017 12:11PMI have a fair amount of this... about 5 kilos. Large pieces and small. I discussed it with my mentor the other day who also has a piece and he said it is a purple form of Melanophlogite. What colors it purple he was not sure. What are your opinions on this? Perhaps this topic should be moved from the fakes and frauds as it is no longer being discussed as that?
PS I am new... nice to meet you all! -Chris
Edited 1 time(s). Last edit at 03/24/2017 12:12PM by Christopher Jolicoeur.
Christopher Jolicoeur March 24, 2017 03:10PMok.... thank you for your thoughtful advice. So the common consensus among experts is that it is in fact a botroydial purple chalcedony? I'm trying to nail this down so that when I sell it I am giving proper information. Thank you. -Chris
Christopher Jolicoeur March 24, 2017 04:53PMThank you Alfredo for that specific information. I do appreciate knowing exactly what it is. Such an interesting material. I believe my mentor shall get demoted for his false claim.
Edited 1 time(s). Last edit at 03/24/2017 04:53PM by Christopher Jolicoeur.
Jolyon & Katya Ralph March 24, 2017 07:25PMThe names 'grape agate' and 'grape chalcedony' have been used for this material on the market, and these are simply trade names.
There are many other 'trade names' that don't accurately represent the mineral species described'
etc etc etc
It's not up to us to create a new scientifically accurate name for this material. We have one already, and it's this.
For trade names, we simply report what names are being used and what the material really is.
Jason Evans April 06, 2017 12:17AMKeith, I too have found those transparent sheaf like crystals in my purple Indonesian chalcedony/botryoidal amethyst and my first thought was stilbite, but looking closer it does not seem right for stilbite, they are more like dumbell or peanut shaped , not like the wheat sheaf form of stilbite. then I looked at some of the photo's that have been uploaded and saw that rice grain and sheaf like crystals are found with this, mine has boith of those forms, and it says it is quartz. I find this really intriguing as I never knew quartz could grow this way, then again I also never knew that quartz could form as botryoidal aggregates of small terminated crystals!
I got this specimen simply because I thought it looked nice, and it's turned into something far more interesting than I expected!
Are there any links to photos of quartz showing this habit?
Clifford Trebilcock April 06, 2017 03:26AMKeith and Jason,
I have also noted these tiny dumbbell shaped crystal forms in a batch of small groups of purple chalcedony balls.
To me the they appear to be made up of tiny quartz crystals. Also noted individual regular shaped quartz crystals
on occasion attached to some spheres. The dumbbell shaped forms remind me of many of the artichoke quartz
crystals from the Francon Quarry in Montreal.Interesting specimens under the scope.
Scott Rider April 06, 2017 04:28PMThose little sheafs almost look like two spheres molded together. I have a few pieces of this material and none have that, but under 40x loop the other spheres do seem to be made up of tiny pyramidal terminations!!!
One of my specimens color range goes from a pasty white, to green to some orange, and finally purple. The white aggregates almost appear to be included by a clay like mineral. And the orange almost appears like iron-oxides... So maybe there is a lot more involved on at this location than we speculate.
The one thing I did notice is that the chalcedony specimens from some parts of Maharashtra, India are very similar. Not the color, as they are usually colorless, but the crystal forms are quite similar. I have a few pieces from there that have pretty much the exact same crystallization from India. Little spheres that appear to be made up of tiny terminated quartz crystals. Cross sections reveal that there could be at least 2 generations, a fiberous acicular formation of chalcedony making up the majority of the sphere, topped off by a 2nd gen, macroscopic "regular" quartz terminations. It is just like the Indonesian material.
Either way, I love these specimens. If you get a good one, they sparkle with a purple glow that is truly unique!!!
Doug Daniels April 07, 2017 12:06AMRemember, in the original post the question was whether such specimens were natural or fake, which is likely why it was posted under "Fakes and Frauds". Maybe it should have been posted in the general messageboard first, but, I can understand why it was done as it was.
Peter K. Szarka April 07, 2017 12:36AMAlfredo's partly correct. This topic should not be in this thread if questioning the legitimacy of the specimens. They are real and have been available for some time now in various colours: yellow, brown, green, gray, purple. Some specimens have gradients of colors across them. Not uncommon to see green, grey and purple together.
I've watched the evolution of this stuff's availability on eBay from the start. These first started appearing commonly from Indonesian sellers on eBay well over a year ago, closer to two. Then YouTube videos started showing up with Indonesians selling the material. Chinese sellers next appeared with them next a few months later. Price went up, size came down on cherry-picked specimens. Finally, a few Americans started listing these in the Fall of 2016. Now there's a flood of this material everywhere.
And here is where I'd consider this topic eligible for inclusion in this thread as a marketing ploy. In person, the vast majority of these specimens look much the same as many other chalcedony dug out of clay. Dull, earthy, with no sparkle. But with the huge influx of grape chalcedony/grape agate occurring early summer 2016, sellers' specimens started taking on great lusters. I suspect oil, silicone, leafshine, water, etc. is being used to 'enhance' them. Not exactly a new ploy in the mineral business. And this is as far as the deception goes I think. The actual specimens are real. But you'll have to watch for 'enhancement'. A soapy water wash of a glistening piece might disappoint a buyer.
Edited 2 time(s). Last edit at 04/07/2017 12:40AM by Peter K. Szarka.
cascaillou April 23, 2017 04:18PMcheck this link for a list of chalcedony treatments:
Joel Dyer April 25, 2017 10:11AMPeter, this has turned into such a lengthy thread that I hope I haven't missed something...
Have you got any of the spherules analyse? XRD might be able to tell you the crystallization degree of the material.
Raman spectroscopy will tell you even better what SiO2 phase this is, partiularly if it contains for example moganite.
I'm in the process myself of starting - or actually continuing - a joint publication project with an experienced mineralogist, concerning moganite & quartz content in Finnish vs foreign chalcedony & some other similar SiO2 materials.
Of course, there have been similar studies carried out already, but no such comparitive work in Finland yet, as far as I'm aware and have been told. Please correct me if this is not true.
So, if you would like me to include some of your material in the study, I'd do it for nothing, but would need a few "balls" of the stuff, preferably slightly different looking / different shades. The same goes for other chalcedony/flint/agate etc chip donations. You will be provided with the anaysis results, no charge. This is a one-off project deal for me, for a limited time only ;-) .
You (whoever it is) can get hold of me via a private message or preferably via firstnamelastname"at"hotmail.com
Edited 4 time(s). Last edit at 04/25/2017 10:14AM by Joel Dyer.
Tim Jokela Jr August 17, 2017 01:58PMHuh? What "cubical formations??
The sparkly material is sparkly because of countless minute quartz crystal terminations.
Interestingly, one piece can have both sparkly and smooth spheres, as well as green and purple.
Fantastic stuff under the scope, photomicrographers need to get busy!
Tim Jokela Jr August 17, 2017 02:18PMStill can't quite wrap my head around what to call this stuff.
The spheres are fibrous in cross section, but surfaces can be composed of crystal terminations, and both sharp single micro crystals and clusters can be scattered upon the spheres, or even make up a matrix for the spheres.
Specimens can be composed of both sparkling exterior crystalline, or smooth, non-crystalline spheres, side by side.
Is it truly cryptocrystalline chalcedony, or crystalline amethyst???
Upon what specific evidence was the term chalcedony chosen by MinDat?
Alfredo Petrov August 17, 2017 05:17PMI don't think a single name suffices, as the material is so variable. Some is botryoidal amethyst, others look like chalcedony or transitional varieties between the two, and the chalcedony can be violet, green, pale grey.... No one name could fit all of them.
aco farid September 27, 2017 06:15PMI have a botryoidal variant from Indonesia but I don't know the type
aco farid September 27, 2017 06:16PMwhat is this
Joel Dyer October 10, 2017 06:40AMI would tend to agree with the comments that the structure of this type of material must vary a fair bit, but would personally call the material (grape) quartz rather than (grape) chalcedony / agate.
I received just recently from Tim Jokela 3 different looking samples: darker purplish, lighter purplish and green. All of the samples show clear crystallinity, with varying sharpness of light refraction.
The lighter purplish material showed clear signs of moganite (10-15%), the other samples just quartz peaks, compared to reference macroscopic quartz crystals.
The light purplish material also showed 2 kinds of crystal habit, sharper terminated elongated crystals in sheath-like formations, and almost pseudocubic form aggregates, quite interesting.
The FOV's here are 0.8mm. Both reflected and transmitted plane-polarised light was used, thus the colour reproduction is not quite true.
John Oostenryk October 12, 2017 09:26PMJoel,
Oh Please DO!
I find this material very interesting- and your imagery would be a great aid to conveying/explaining the current description!
For a humorous aside~(and nothing else!) The appearance of the crystalline surface- immediately brings to mind a common formation in the "Keokuk geode region" sedimentary geodes.
A thin layer of chalcedony overgrowth of the quartz crystals. These are like an inside-out one... in MICRO scale :)-
Fryxell Geology Museum
Owen Lewis October 12, 2017 09:47PMI've been following the recent posts here with interest. I would agree that *some* does not look like chalcedony. Is it possible that some occurrences are quartz and some are chalcedony?. Both amethystine quartz and amethystine chaldedony are reliably identifiable by simple testing and basic gemmo tools.That'd my my start point for further enquiry anyway.
If one of you guys that have some break off a a piece or two of the partly transparent spheroids (likely quartz), You can test for:
- Fracture lustre.
- Optic character
Get a piece polished optically flat. and you can get the (different) RIs for both quartz or chalcedony specimens and sort them out with confidence. I would not want to rely on hardness and SG testing in this instance.
Sorry, only registered users may post in this forum.
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2018, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2018, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.