www.photomacrography.net :: View topic - Lava rock with filled voids
www.photomacrography.net Forum Index
An online community dedicated to the practices of photomacrography, close-up and macro photography, and photomicrography.
Photomacrography Front Page Amateurmicrography Front Page
Old Forums/Galleries
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Lava rock with filled voids

 
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> Technical and Studio Photography -- Macro and Close-up
View previous topic :: View next topic  
Author Message
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 17874
Location: Richland, Washington State, USA

PostPosted: Sat Sep 22, 2012 12:45 am    Post subject: Lava rock with filled voids Reply with quote

Today I had a tree stump ground out of my backyard.

The grinder kicked up a few rocks, breaking most of them open in the process.

Most of the broken rocks did not strike me as interesting, but this one did.

4 cm wide:


A closer crop:


Closer yet:


I live on a plain formed by cataclysmic floods at the end of the last ice age. As a result, the rocks in my yard are a thoroughly mixed jumble plucked randomly from probably several hundred square miles. A fair number of them came from ancient lava beds to the northeast, and many of those contain empty voids formed by gas pockets when the lava erupted.

This particular rock, however, seems rather more interesting. It appears to have started life as lava with voids, but then many of the voids got completely filled in with some brown crystalline material and a few of them just accumulated a thin white deposit on one side.

If anybody knows more about this material, I would be grateful to learn.

In the meantime, it was another opportunity to practice using Magic Lantern. This was 21 frames at f/8 shot with StepSize 1 and 3 steps per frame, using a Canon EF 100 mm f/2.8L IS USM macro lens on a Canon T1i camera. 1/3 second exposure time with incandescent illumination. Just camera on tripod -- no tether or rails. Very simple setup!

--Rik
Back to top
View user's profile Send private message Visit poster's website
Craig Gerard



Joined: 01 May 2010
Posts: 2877
Location: Australia

PostPosted: Sat Sep 22, 2012 1:17 am    Post subject: Reply with quote

Rik,

I hope one of our geologists solve this mystery. It's a fascinating piece of 'rock'.


Craig
_________________
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"
Back to top
View user's profile Send private message
Pau
Site Admin


Joined: 20 Jan 2010
Posts: 3807
Location: Valencia, Spain

PostPosted: Sat Sep 22, 2012 3:28 am    Post subject: Reply with quote

The gas vesicles filled with minerals are called amygdules. Its composition may be highly variable, and often not related with the composition of the rock or original magma.

Yours seems an iron rich mineral partialy ozydized, but it's impossible to determine a mineral this way.
_________________
Pau
Back to top
View user's profile Send private message
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 17874
Location: Richland, Washington State, USA

PostPosted: Sat Sep 22, 2012 10:53 am    Post subject: Reply with quote

Thanks, guys!

Pau, many thanks for the information. Just having that word "amygdules" is very helpful for looking up more.

--Rik
Back to top
View user's profile Send private message Visit poster's website
microcollector



Joined: 14 Mar 2007
Posts: 244
Location: Port Orchard, Washington

PostPosted: Sat Sep 22, 2012 9:18 pm    Post subject: Reply with quote

Last Sunday I was collecting in the Capitol Forest near Porter, WA. This was in basalt quarries where we were looking for zeolites. Some of the basalt had a weathered rind with similar looking void filling to your piece. The inner, unweathered voids had a clay mineral in them. These are not visually identifiable. This mineral will weather to various iron oxide minerals. The zeolites we found were cowlesite, analcime, thomsonite, phillipsite, and chabazite. The clay minerals were black, brown, and a bluish gray which made the colorless minerals take on the color of the clay mineral.
Doug
_________________
micro minerals - the the unseen beauty of the mineral kingdom
Canon T5i with Canon 55 250mm zoom as tube lens set at 200mm and Mitutoyo 5X or 10X M plan apo objectives.

My Mindat Mineral Photos
http://www.mindat.org/user-362.html#2
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> Technical and Studio Photography -- Macro and Close-up All times are GMT - 7 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group