What is this obsidian w/purple flash

[jamesp]

Thses were given to me recently by my mentor.Bill say's they are over 40 years old.
I am curious about the material.Please help



I believe this is also obsidian

[paulshiroma]

Sheen obsidian. You can find a lot of it up in Davis Creek, CA. I bought several boxes worth from Tony and the Hand-2-Mouth mining guys. Great stuff. Lots of fun to slab and tumble. The middle photo is mahogany obsidian. Great looking pieces, James!

[bhiatt]

showoff...those are sweet

[jamesp]

Guilty showoff it is.Those were knapped the old way w/out being knapped from slabs.
Thanks Paul.I felt certain it was desirable material.

[Pat]

Purple is sheen. Sheens also come in blue, silver, gold, and probably other colors

Your red and black is mahogany obsidian.

[jamesp]

And the photos do not do it justice.I wonder why it sheens Pat?

[helens]

That rainbow obsidian on the top left is OMG beautiful!! I always wondered HOW they attach a rounded bottom like that to a spear... looks like it would just fall right off??

[helens]

James, have you seen these before?
www.texasbeyondhistory.net/alibates/index.html

Alibates Flint... look at those colors, from the Texas 'panhandle'

[Pat]

James, I don't know; possibly mica inclusions. Hope somebody pops up with an answer.

[jamesp]

Somebody will know Pat.I would guess that it has to do with mangenese or selenium.Glass made out of sand w/those metals turn purple i guess at manufacture.Glass from Jacksonville(NE Florida) is famous for this phenom.Lots a purple bottles and insulators in N FL/S GA.

I am only guessing though.

[jamesp]

I have heard about the alibates material Helen.Never knew it was so attractive.Killer article.

Ancient quarry sites like that are gold mine for tumbling material since the early guy went and collected the pretty stuff and broke it to pieces for thousands of years and even heat treated some of it so lazy tumblers folks can fill their buckets w/it.

That is a excellent article and a typical archeology expose' of native folks.

My fascination that these eary people were attracted to pretty materials.That they had an eye for color.And the pieces i find in the piles are such high grade materials that i never can find the vein or source they got it from.

[Sabre52]

I picked up a few pounds of Alibates Flint rough at the Federicksburg knap-in a couple of years ago. It's very solid but does not vary a lot in color like Flint Ridge does, mainly purples, reds, whites and pinks in bands. I can see why the Amerinds liked to work it as it's cool looking stuff. Haven't slabbed any yet for cabbing but it take a fine polish n the tumbler....Mel

[Deleted]

The sheen in obsidian is probably not selenium or magnesium. The sheen is a prism effect and is not due to the color of the glass. This is evidenced by the directional component of the sheen. If it were color, then the angle would not be important.

Volcano world at OSU tells us:

A certain amount of water always is present in obsidian. Very small inclusions of water vapor in the form of bubbles often are trapped in the glass. Tiny gas bubbles that have been stretched nearly flat along the flow layers in obsidian generally cause the reflectance of gold sheen and silver sheen obsidian. Some of these bubbles are visible to the naked eye. The bubbles can be seen readily with a strong magnifying glass or a microscope.

Which, BTW explains the off-gassing of tumbled obsidian.

Jim the clear stuff is called "midnight lace" obsidian and is found in Oregon.

I hope this was useful.