[Rockhounds] petrified wood from Glass Buttes, OR?

[Earl R. Verbeek]

Hi Don,

I've seen obsidian flows that incorporate material that pretty well matches 
your description, where upon extrusion of the magma the gas-rich flow layers 
solidified as fine-grained rhyolite and other layers solidified as true 
glassy obsidian.  Parts of such material do indeed resemble petrified wood 
at first glance.  But hey, you're the optical min guy, so break off some 
frags from various layers and see if they're isotropic, and also look for 
microscopic, dustlike inclusions of opaque phases such as magnetite (if it's 
obsidian).  It's a start....

                Cheers-   Earl

----- Original Message ----- 
From: "DonH" <donhalterman at verizon.net>
To: <rockhounds at lists.drizzle.com>
Sent: Thursday, November 08, 2007 11:26 AM
Subject: [Rockhounds] petrified wood from Glass Buttes, OR?


>
>
> Howdy,
>
> One of my neighbors, in return for giving him some knappable obsidian I 
> bought at the Barter Faire, gave me a large piece of material from Glass 
> Buttes.  I said, "oh wow, petrified wood!"  He said no, it's obsidian. 
> Now, it is about 2 ft. long and shaped like a tree section, dull brick 
> red, with ring structure and little openings or channels (xylem? phloem? I 
> can't remember my biology!) arranged in regular patterns.  The rings are 
> eccentrically shaped, not really rings at all, but they are layered 
> distinctly from inward out.  On the outer surface, the breakage pattern 
> reveals thin layers.  Everything about this says wood to me.  But he says 
> there are huge formations of it near Glass Buttes.  I didn't want to 
> argue.  Perhaps he is confusing this with mahogany obisidian (which has a 
> more orange hue and is glassy, not dull?)  Does this sound like something 
> anyone has seen at Glass Buttes?
>
> I can provide a photo later.
>
> best,
> Don