Quick Links : Mindat手册 The Rock H. Currier Digital Library Mindat Newsletter [Free Download]

主页关于 Mindat Mindat手册 Mindat的历史版权 Who We Are 联系我们于 Mindat.org刊登广告

捐赠给 Mindat Corporate Sponsorship 赞助板页已赞助的板页在 Mindat刊登广告的广告商于 Mindat.org刊登广告

Learning Center What is a mineral?The most common minerals on earth Information for Educators Mindat Articles The Elements The Rock H. Currier Digital Library Geologic Time

搜索矿物的性质搜索矿物的化学 Advanced Locality Search 随意显示任何一种矿物 Random Locality 使用minID搜索邻近产地 Search Articles 搜索词汇表更多搜索选项

Mindat手册添加新照片 Rate Photos 产区编辑报告 Coordinate Completion Report 添加词汇表项目

Mining Companies 统计会员列表 Mineral Museums Clubs & Organizations 矿物展及活动 The Mindat目录表设备设置 The Mineral Quiz

照片搜索 Photo Galleries Search by Color 今天最新的照片昨天最新的照片用户照片相集过去每日精选照片相集 Photography

Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

Fakes & FraudsGreen volcanic glass - is this natural or artificial?

30th Jan 2011 09:11 UTCchong wei khee

The seller told me this is Green volcanic glass.

Does any one knows whether this Green volcanic glass is natural or artificial?

Thanks.

30th Jan 2011 09:18 UTCchong wei khee

Hi,

Photo of another sample of green volcanic grass.

Pls advise me whether these glass are natural or artificial. Thanks million.

30th Jan 2011 11:00 UTCErik Vercammen Expert

Looks artificial. Green obsidiane is opaque.

30th Jan 2011 11:31 UTCGuenter Blass

Hi,

it can be but must not!

In the Eifel-Mounts, Germany, it gives such green or blue volcanic-glasses.

see also extraLapis 34, Eifel, 2008 the article from

H. LOCKER (2008): Edelsteine der Vulkaneifel - extraLapis 34, page 80-86.

Günter Blaß

30th Jan 2011 12:23 UTCchong wei khee

Thanks Guenter Blass and Erik Vercammen !!!

I do not have extraLapis 34, Eifel, 2008 and I cannot read German...:)

Do you means this could be natural? Can share your experience and knowledge with me? Thanks?

30th Jan 2011 12:40 UTCJolyon Ralph Founder

This glass is artificial.

30th Jan 2011 13:34 UTCWayne Corwin

Man made glass.

Wayne

30th Jan 2011 14:52 UTCPaul Brandes 🌟 Manager

This is artificial; natural obsidian does not come in this shade of green, even from the Eifel Mountains in Germany.

30th Jan 2011 15:08 UTCChester S. Lemanski, Jr.

This material is manmade and is supposed to be the fused product of Mt Saint Helens volcanic ash. Since it now pops up around the globe, it is probably not all from Oregon or even from volcanic ash.

30th Jan 2011 16:12 UTCAnonymous User

Artificial. I have seen green obsidian from mexico but it was opaque.

30th Jan 2011 17:13 UTCGuenter Blass

Hello,

I say this glass can be artifical or naturel.

In Eifel-Mounts it gives glass with a broad palette of colours (yellow-brown, light-blue, darker blue, light green, darker green). More often than not they are transparent.

I will try to send a pic, next days.

Günter Blaß

30th Jan 2011 17:44 UTCLuca Baralis Expert

I got a specimen of raw "chinese obsidian" looking very like your sphere. Truely it (mine) is glass.

May be you can find something about "green obsidian" in Mindat messageboard.

30th Jan 2011 18:44 UTCAdam Kelly

Manmade glass.

I have natural green obsidian from Ore Vada sp?, Nevada but it is very opaque.

31st Jan 2011 00:03 UTCAnonymous User

Sorry to say, but from the pictures that you have posted it is definitely man made.

As many have previously reported coloured obsidian tends to be more opaque. This can be caused by tiny microscopic inclusions of other minerals (feldspar, amphibole, biotite, quartz) called microlites (not the mineral). They can be observed under a microscope as thin rectangular, sometimes equant crystals that can sometimes form bands and give obsidian its characteristic colour. In the case of dark green obsidian the colouration is caused varying amounts of Fe and Mg. The green colouration can also be achieved as some gas bubbles (vescicles) remained in the lava flow during crystallization creating what is called "rainbow obsidian". You can check it out (for a picture reference) on wikipedia.

Hope this helps

31st Jan 2011 18:28 UTCGuenter Blass

Hi all,

here a pic with blue total transparency volcanic glasses from Eifel Mounts.

More pics later.

Günter Blaß

31st Jan 2011 22:09 UTCAmir C. Akhavan Expert

Very beautiful. I wouldn't have expected that.

Scale?

I guess the available amount would not allow the economical production of glass spheres, though. ;)

(actually, if these were in my collection, I would freak out if anybody with lapidary tools got near them :D )

1st Feb 2011 10:50 UTCGuenter Blass

Hi Amir,

the bigest exemplar on the pic is round about 1.5cm.

It gives rarely also such with 2.5cm.

Also it gives gemstones up to 4ct.

Günter

19th Feb 2011 21:04 UTCUwe Kolitsch Manager

The natural Eifel glass with blue to green colour is very rare and forms at the contact between xenoliths and lava, usually as layers only a few mm in thickness.

24th Feb 2011 15:15 UTCKristi Hugs

*sigh* i have to agree with those who say it is glass and man made. It annoys me that many vendors think that glass, man made or not, can be called Obsidian. See this a lot in the vendors I deal with and online.

24th Feb 2011 17:07 UTCAlfredo Petrov Manager

Incidentally, with regard to the beautiful Eifel glass, whereas they are natural, technically I wouldn't call them "obsidian" because that's an extrusive rock name for rapidly cooled glassy lava, and the Eifel glass is small melted xenoliths, having neither the scale nor the genesis required to be obsidian. So I still believe that colourful transparent obsidian does not exist.

24th Feb 2011 18:00 UTCErik Vercammen Expert

I'm not sure about it, but the beautiful green 'glasses' from the Eifel may be lechatelierite, xenolitic quartz crystals molten by the heat of the lava.

8th Mar 2011 04:17 UTCKimberly Hamm of USA

Hey ya'll my name is Kimberly Hamm. I live in Michigan and quite a few years ago I was swimming at the beach and stepped on what I thought was just glass.....I have since been told it is Obsidian Volcanic glass....I have sent pictures to a Geologist in Arkansas when I was living there and she said it was but just wouldn't believe I found it in Michigan......but is she had done her research she would have known that the Hopewell Indians traded up and down the shore line of The Great Lakes ......(where I found my Obsidian).....I have attatched a picture of my Obsidian...please let me know what you think....one_tripp@yahoo.com..........

8th Mar 2011 23:41 UTCPaul Brandes 🌟 Manager

Well Kimberly, one of your three names (obsidian/volcanic/glass) is correct. To me, it looks like a piece of green glass that fell off a ship and got tumbled around in the Great Lakes before washing up on shore. Usually, green obsidian is more gray/green in colour and very opaque; the Burns green obsidian in Oregon comes to mind.

9th Mar 2011 01:11 UTCAlan Barnes (2)

The blue obsidian from Eifel is very interesting Guenter. Does the blue colour arise from inclusions of other elements in the lattice rather like it does in blue diamonds, or is it from natural radiation?

Alan

9th Mar 2011 11:59 UTCUwe Kolitsch Manager

"The blue obsidian from Eifel ..."

It's NOT an obsidian, just a blue natural silica-rich glass.

9th Mar 2011 12:34 UTCSpencer Ivan Mather

I have seen plenty of this artificialy made glass in garden centres, and a friend of mine ground a piece down so we could see what the included crystals were, they turned out to be similar to leucite.

Spencer.

14th Dec 2012 22:44 UTCJay Taylor

I have heard of some killer Blue Volcanic glass from Indonesia. The only issue that I cannot resolve is whether it has been heat treated or not. My guess is that it has, but indications are that it is not man-made.

jt

15th Dec 2012 02:28 UTCJosé Zendrera 🌟 Manager

And ...what you think about this? Is offered in e-Bay by some serious Pakistani dealers, presumably from Kaghan Valley, Pakistan. Usually it comes with some white (riolite?) remains.

Green obsidian?

Kaghan Valley, Mansehra District, Khyber Pakhtunkhwa Province, Pakistan

3 x 2 x 1,4 cm

15th Dec 2012 10:40 UTCRock Currier Expert

Looks like a man made glass.

15th Dec 2012 13:17 UTCOwen Lewis

Yes it does. More than a bit. But not to jump to conclusions.... Jose, is it SR.ADR ir DR? It not SR, then is pleochroism detectable and in what colours/tones, S/M/W? Crystalline inclusions?

Worth a close look?

15th Dec 2012 19:52 UTCJosé Zendrera 🌟 Manager

Owen, I can not answer because I have not any specimen, I knew about this Pakistani material just for seeing it in e-Bay but I never bought a sample. Appearance and color are really suspicious but I can not speak properly without knowing the material directly.

In the Spanish FMF forum there is also a discussion about this and most expert opinions think that is a fake:

http://www.foro-minerales.com/forum/viewtopic.php?p=86715#86715

2nd Mar 2013 21:40 UTCfarshid

Hi friends

What do you think about this?

2nd Mar 2013 21:54 UTCJolyon Ralph Founder

Artifical.

2nd Mar 2013 21:59 UTCfarshid

Why ? Plz tell me your reasons.

3rd Mar 2013 02:04 UTCAdam Kelly

Years of seeing nearly identical pieces

3rd Mar 2013 09:39 UTCfarshid

Hi Mr Blass

I need your help

Plz give me your email address

17th May 2013 03:53 UTCLeor Goldberg

I suspect that it is made from volcanic ash that was smelted. That could easily be. I saw an ad in national geographic once that said this. The title was something like "Mt. St Helens ash Gem" or other. Either way, it's not what you were looking for.

23rd Feb 2014 00:33 UTCTom Kap

Definitely man made in China

Inclusions if I remember correctly is wollastonite .

The Story about Mt St Helken vocal antic ash being use is a load of crap.

Used by sellers to misrepresent true origin .

Lots of "strawberry Qtz" that is just cinnabar infused glass on the market now as well

Regards tom kapitany

28th Feb 2014 02:59 UTCMike McEachern

For those of you interested in green obsidian, you might want to read the article "The Pachuca obsidian source, Hidalgo, Mexico: A geoarchaeological perspective" by

Alyson Lighthart Ponomarenko (Geoarchaeology Volume 19, Issue 1, pages 71–91, January 2004). It describes the archeological history and geological placement of obsidian flows in Sierra Las Navajas, “the Pachuca obsidian source" which was an important source of obsidian to Middle Americian cultures for thousands of years. Much of the obsidian from this area is green and the type V obsidian in particular is transparent Coke bottle green.

24th May 2014 15:47 UTCjerry

Ijust found some large pieces of green V. glass here in town ,yes dome of it is opaque ,but there are also some portions which r alsmost gem quality in translucence

18th Jul 2014 03:04 UTClorna kuzina

Yes it was around since at least 400 bc to 600ad . It was reveered to start fires and mostly used by the upper class in the Mexico Archipelico regions and the dark cobalt color was also used to make sensors that have been found in gravesites also with a scriptlike writing etched in as I own , found in the 80's. Mine has some green mixed in the mostly blue obsidian with a shiney wall in it.

22nd Sep 2014 18:19 UTCDani Watkins

I wonder if anyone can help me. 8 years ago my ex partner worked with stone recieving deliveries from mines on a regular basis. One day he came home with a green rock once polished it looked like green glasd like rock. I tried to add a picture but says the file is too big. Thanking you in advance

31st Oct 2016 02:15 UTCIstian

Thought I'd share this one which is really intriguing and exciting at the same time hehe because of its... oddity? hehe

I recently bought a chalcedony from my trusted indonesian middleman vendor. Out of curiosity, I asked him about Natural Obsidian / Volcanic glass from his country because I see some of it being offered online in different nuances of blues and greens. He said that yes it's naturally mined and there are two types of it -- the obsidian glass usually slab/rough form and the "cyclop papua" which are spherical rough forms. But he says I have to beware though because some artificial man-made glasses are also being sold as "obsidian" in the market. And so I asked him if he could find me a natural volcanic glass obsidian rough. The real stuff. --- and after a few weeks of sourcing, he showed me this greenish gemmy obsidian rough with a few white cotton-like spheres inclusion/patches. He says that his source miner & seller have only this piece because it's Langka (or "rare" in english) and out of his few chunks of obsidian roughs, this is the only one with white spots he has and it comes by not very often.

A Gemmy Green Snowflake Obsidian? Hmmm... It could be :)-D hopefully :-D

31st Oct 2016 09:48 UTCŁukasz Kruszewski Expert

Also looks artificial to me, although a bit hard to say basing on the reworked specimen (no geo-context).

31st Oct 2016 13:45 UTCSteve Hardinger 🌟 Expert

Certainly looks like slag glass to me.

31st Oct 2016 18:42 UTCUwe Kolitsch Manager

Clearly artificial glass.

"He said that yes it's naturally mined and there are two types of it"

They say that all the time...

31st Oct 2016 19:15 UTCJay Taylor

Hmmm If it is glass, why would it contain big white inclusions? I thought glasses are supposed to be clean except for some gas bubbles. colorless gas bubbles.

jt

31st Oct 2016 19:33 UTCDavid Von Bargen Manager

If glass is cooled too slowly, it has a chance to devitrify and form inclusions of cristobalite or tridymite.

31st Oct 2016 19:57 UTCAndrew Debnam 🌟

these inclusions or impurities are quite common in the glass making process particularly in antique - ancient glass. They are generically referred to as frit although the term is widely used for other forms.

frit https://en.wikipedia.org/wiki/Frit

31st Oct 2016 20:01 UTCAlfredo Petrov Manager

What Uwe said. This story about the so-called "natural" glass from Indonesia has been around for a long time already.

1st Nov 2016 00:32 UTCjt

Thanks for the link --- I read it and a part says "shows numerous white flecks of unreacted silica and a large number of vesicles where gases had formed." - based on the photo provided by another poster, obviously the white balls inclusion isn't just a white fleck. it's bigger than a fleck of silica or any other element... and I don't think indonesia are that knowledgeable about frit and ancient glass-making stuff (no offense indonesia)

jt

1st Nov 2016 17:58 UTCJyrki Autio Expert

This is self collected from Atacama and I would say natural one to see for a change. Picture was once already erroneously in quartz thread which was my mistake.

Small blue dots seem to be cordierite and even smaller needles not visible in picture probably sillimanite.

Any idea what causes the blue color in glass? The glass was not probed.

1st Nov 2016 18:09 UTCAndrew Debnam 🌟

Cobalt can produce blue in glass, not sure if that is the case here.

1st Nov 2016 18:16 UTCAlfredo Petrov Manager

You might ask Dr Jaroslav Hyrsl in Prague. A long time ago he had studied some sillimanite-bearing glasses from Chile. Might well be the same material.

17th Nov 2016 01:56 UTCAlexander Ringel

This blue in this sample is most probably caused by microscopic particles. Rayleigh scattering. You can test it. If you place a light behind it and the blue becomes brown or yellow its definitly Rayleigh scattering.

17th Nov 2016 07:52 UTCJoel Dyer

Hi Jyrki,

Sorry I forgot again to send you the epoxy preparate & other obsidian pieces I polished, prepared, investigated & had analysed. Will mail them to you...

Below's a closeup picture of a 1-1,5mm slice of the blue-gray obsidian in epoxy. Even using my Tiyoda 65x smack-up against the surface and the Lomo NA 1,25 condensor lens it's hard to get enough halogen light beam through the opaque material. Light is transmitted plane-polarised.

The FOV here is around 133um. As you can see, the material is full of uneven, somewhat swirly impurities. I can't tell what the minute dark green-looking inclusions are, because they're simply too small. There are many cordierite and certainly some light-coloured sillimanite and / or andalusite, as well as possible some spinel or other unanalysed phases.

I'd tend to agree that it's some sort of Rayleigh scattering that causes the bluish colour, though I'm just an modest-level amateur, no expert in any way.

Cheers,

19th Nov 2016 11:04 UTCJyrki Autio Expert

Thank you all for your insights. This one seems reasonably well explained now.

Go to top of page