Blue Rock-Maybe Blue Obsidian?

[NorthSlope_Alaska]

Found a bunch of this scattered on the surface. Located with Basalt in the mountains above Ellensburg Washington.
Any Ideas?

 

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[extractor]

looks like agate i think.

 

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[Nashoba]

Here is an idea....Break a piece with a hammer.....if it sounds and shatters like glass, you have yourself some dark blue obsidian.....Some may be rainbow as well...Or if you are a knapper or know someone who makes arrowheads and such, let them have a crack at it...Pun intended
~Nash~

 

[NorthSlope_Alaska]

Re: Blue Rock-Maybe Blue Obsidian? - Final Update

http://sourcecatalog.blogspot.com/2009/10/newest-addition-to-our-list-of-obsidian.html

Park Creek Tachylyte: Washington's Newest Obsidian Source
The newest addition to our list of obsidian sources in Washington is the Parke Creek tachylyte source. Thanks go to Adam and Joel Castanza for their efforts in tracking down source samples from this new outcrop located in the Parke Creek area northeast of Ellensburg and for sending them to the lab for analysis.

But first off, what's a tachylyte? And how is it different than the usual obsidians that are found in the Northwest? Because obsidian is a textural term, the composition of obsidian glasses can vary considerably. Most commonly, the silica content of obsidian falls into the rhyolitic range and the SiO2 content will be approximately 70 percent. Tachylitic obsidian, on the other hand, has a silica content closer to 50% (basaltic) and is commonly found as chilled margins of flows, sill, or dikes. These basaltic glasses are usually dark and very opaque and are easily distinguished from their rhyolitic counterparts by their elevated contents of titanium, manganese, and iron. In addition, the basaltic glasses are usually full of phenocrysts and most often are poor candidates for the manufacture of artifacts.

What makes the Parke Creek tachylyte unique is its relatively good flaking characteristics compared to those of most basaltic glasses. Interestingly, it turns out that there are several other tachylyte sources in Washington that also share this flaking quality. However, the size of available nodules from all of these Washington tachylyte sources tends to be fairly small and we only very occasionally run across them when analyzing archaeological collections.
Posted by Craig E. Skinner at 3:42 PM



This coming April my son and I will be heading up into the mountains to collect samples for distribution. I will post when we have some available samples
Regards
Joel Castanza

 

[Goodyguy]

Awsome post Northslope!

May I be the first to request a sample of of your newly discovered "Parke Creek Tachylyte"
Congratulations on your discovery!

GG~

 

[niffler]

Looks like OPAL to me...Opal will flouresce(?) greenish. I have some nice opals from here in southern Idaho.

 

[Arid-Zone-A-seeker]

Hey North s,,,, Bring back a truck load! want to trade some for some p-wood?

 

[NorthSlope_Alaska]

Just a quick update to let you all know I haven't forgotten you! There is still snow in the Mtns and it looks like maybe late April before I can get to my spot. The hunt for this material is lengthy. It's a 2+ hour drive each way, plus surface hunting the material. So what I have on the first trip may be very limited.
JC

 

[BigDan]

I'm thinking blue chalcedony

It looks like the color is rather milky. That is a trait of chalcedony.

I am far from an expert. But that's my guess.