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Tektites with Brown

Posted by Gordon c De'young  
Tektites with Brown
August 25, 2009 12:50AM
We are finding these in Oregon,So far all the test are saying they are indeed tektites.I am however afraid to send off the brown colored ones.I think they need to cut them open?Dr Weller of Cochise college, in Arizona and others are performing the test.Unfortunatly we are going to have to wait to find more the winter weather help's in washing the silt off of them and the ground freeze pops them up out of the ground.So far we have two locations 20 miles apart as a bird fly's.These have been cleaned currently we have 3 five gallon buckets full of them.I suppose besides woodcarving ill be cleaning tektites(but will leave some dirty for the testing) we also have alot of the silty soil they are found in.The samples pictured from 2.7cm to 4.2cm the Brown colored one measures3.2cm
Attachments:
open | download - tektites4 006.JPG (716.7 KB)
open | download - tektites5 006.JPG (473.3 KB)
open | download - tektites5 022.JPG (837.9 KB)
Re: Tektites with Brown
August 25, 2009 03:06AM
Im sorry but I have to say no to the Tektites. What you have there are obsidian bombs the giveaway is the brown streaked one. It is a dead giveaway for mahogany obsidian.

Sorry


Byron
avatar Re: Tektites with Brown
August 25, 2009 10:23AM
    
Tektitic glasses should be very differ from obsidianes by their water contents. Tektites are almost dry, while obsidian contains 1-2 % H2O or more (perlite glass).
So you need in precise water content determinations in your glasses.

Besides that, finding of such phases as moissannite or native metals (Si, Fe, Ni etc.) in heavy concentrates from your glass may to confirm its tektitic nature.

By the way, I never saw "obsidian bombs". From other hand, these objects are similar to some indochinite specimens.

Kind regards,
Pavel
Re: Tektites with Brown
August 25, 2009 12:36PM
I agree with Byron that these are obsidian pebbles, abraded and etched by surface weathering.
avatar Re: Tektites with Brown
August 25, 2009 01:04PM
    
Yes, they may be pebbles (with little bit strange structure of surface for water abrasion). But really not a bombs.

In any case water content determination isn't hard accessible and expensive test. Oregon isn't Upper Volta. ;)
Re: Tektites with Brown
August 25, 2009 02:10PM
Gordon, I am curious as to the fractured sample with the two light grey spherical inclusions. These should be tested. There is a possibility that they may turn out to be the high temperature silicon dioxide cristobalite and this may verify Byrons idea. So I would encourage you to have these areas analyzed. Steve.
avatar Re: Tektites with Brown
August 25, 2009 02:31PM
    
Steven is quite right! Such spherulites (blue arrowed) are very often observed in obsidians ( and synthetic glasses) and consist of different silica polimorphs (cristobalite, tridymite) and anortoclase mixture (both silica and feldspar are fibrous). By the way similar, but much more smaller, spherulites with tridymite I observed in "Libian glass" tektites also. Tektites had cool too fast for large spherulites formation (as we can see on the photo), but may to contain them (especially in large/massive tektite pieces).

If this material really contain tektite particles, only two from the picture are similar to tektites (yellow arrowed).

From my point of view, it is enough to break such "tektite" and obvious obsidian specimens and compare outer view of broken surfaces of both. If they are the same, all material is obsidian.





Edited 1 time(s). Last edit at 08/25/2009 02:37PM by Pavel Kartashov.
Re: Tektites with Brown
August 25, 2009 03:07PM
Ok not bombs but still obsidian.

Byron
avatar Re: Tektites with Brown
August 25, 2009 03:08PM
    
Hi Gordon

It is almost certainly obsidian. Here is a photo that shows obsidian with cristobalite from California;
[www.mindat.org]
Notice how the crystals are radiating spheroids in both photos.

If you need more here is a great test that most of us non scientist types can preform;

from O'Keefe, John A 1976 Tektites and Their Origins

A tektite is a natural glass, usually black, but sometimes green, brown or gray, which occurs in lumps, usually a few centimeters in length, having no chemical relation to the local bed rock. Tektites are broadly similar to some terrestrial volcanic glasses (obsidians); they can be distinguished by heating to the melting point with a blowpipe or a blowtorch. Obsidians turn to a foamy glass, while tektites produce a few bubbles at most, because of their much lower content of water and other volatiles. Under the microscope, obsidians are seen to have abundant microlites (microscopic crystals); tektites have essentially none.

Here is a excellent article that shows pictures of the results of the blowtorch test;
[www.meteorite-times.com]

I actually get that same question several times a year. Unfortunately in almost 15 years I have never had any pass the test.

Good luck with your test.

Mike Jensen
avatar Re: Tektites with Brown
August 25, 2009 04:41PM
    
The similar in simplicity test is:
take 1 g of tested specimen crushed in powder and heat it up to 1000o C in furnace. After cooling weigh it. If you have obsidian, it will give 900 mg or less. If you have tektite - its weight still stay around 1 g.

Really it is hard busines to look for tektites along Western coast, too much obsidian spread in this region.
avatar Re: Tektites with Brown
August 25, 2009 06:03PM
    
I still think Tektites, but the brown one is odd.
Can't wait to see what the results of the tests are!
Re: Tektites with Brown
August 25, 2009 06:26PM
No blowtorch or fancy apparatus necessary - a kitchen gas flame is quite sufficient for this test. And those of you who have an electric range in the kitchen should toss it and get gas flames - they are just simply way too useful for mineralogical tests!
Re: Tektites with Brown
August 25, 2009 07:32PM
    
Ah yes, the kitchen gas flame. I still remember well my exploits when I was about 12 years old, generating a whole lot of metallic mercury by heating mercuric oxide over the stove. A lot of the mercury condensed in the test tube. I can only imagine how much didn't, and how much I inhaled. Kids, don't try this at home!! ::o --Ken
Re: Tektites with Brown
August 26, 2009 12:05AM
Back in May of this year a professor from Southern Oregon University,Dr. "Smede" sent off a few of my tektite samples the folowing is a (exert)from a letter in responce from Dr Fiske.of the," Department of Mineral Sciences National Museum of Natural History Smithsonian Institutite"in the {qoute} "The box arrived today,and i showed the stone to Linda welzenbach,She's not a tektite specialist,but on first glance she said it sure looks like a tektite.So i would bet that it was a tektite.{end qoute} Still waiting on paper work as well as Dr Weller, and his test results.
Re: Tektites with Brown
August 26, 2009 01:14AM
So she admits she isn't a specialist; she just looked; did no tests... and then proclaimed it "sure looks like a tektite". Why am I not impressed?
Please, Gordon, forget about museum opinions; just do the necessary tests yourself - It isn't difficult.
avatar Re: Tektites with Brown
August 26, 2009 11:45AM
Alfredo,

Sadly it IS very difficult to do a test, however simple, that could turn your valuable tektites into worthless obsidian.

Such is human nature.
Re: Tektites with Brown
August 26, 2009 03:10PM
Hello Alfredo, would you please explain. I tried this with a small sample i stood over the stovef or over a half an hour holding the specimen in big needle nose pliers.Nothing exciting happened, i did manage to drop it and it cracked in even smaller pieces.I then placed the even smaller piece over the fire.No foaming and i dont really want to call what it did bubbling either it seemed more like plopping and now it has tiny lil pimples.A few of them not many.Ill wait for the smithsonian and Dr Weller, Of Cochise college to do the real testing.After all theres no real hurry anyways.I dontplan on going back to the source until the spring anyways.For me its woodcarving time(i am a full timewoodcarver) thanks everyonefor all your wonderful input.If and when these are indeed verified as being tektites i will be giving many away to collectors who ask.PS..Alfredo. i was mearly pointing out how the head of the department at the Smithsonian Institute thought they might be tektites Wouldnt you agree she must have an educated guess? i mean that is a respectiful post she has isn't it? Also Dr Friske, also says at first glance they appear to be,yes i know apperance can mean many things but you have to remeber how many of these have these people actually seen and the respected positions they hold at the Smithsonian,Iforgotto mention Dr Smede,of Southern Oregon University, did perform test and they came back positive he simply sent some off to the Smithsonian, because of the number of samples found and the location.
Re: Tektites with Brown
August 26, 2009 05:00PM
Gordon, probably your sample didn't get hot enough, because the sample was too big, and the pliers conducted too much heat away. Smash a big piece and select a sharp little splinter, and hold that in the flame with a thin iron wire. (Hold the iron wire with a wooden clothes pin, so you dont burn your fingers.) I think you'll get better results, and it will take only seconds; no need to stand there a long time. Good luck!
Re: Tektites with Brown
August 26, 2009 11:48PM
Thanks,Alfredo i did it this way and the results were bubbles,no rapid foaming stuff.
Re: Tektites with Brown
August 27, 2009 01:16AM
Bubbles, and even pimply swellings, indicate a small water content in the glass. (Foaming would have meant a relatively big water content, as in perlite.)
Warning: Testing stuff becomes addictive! Have fun.
Alfredo
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