BajaNomad

Geology I D anyone?

vgabndo - 4-22-2014 at 10:35 PM

This rock about the size of a double extra large egg wouldn't let me walk past. The embedded reflective material kept flashing at me as I passed.



As each face of the angular embedded material is faced correctly into the sun it reflects brightly. As you see in the images, when not aligned, the surface looks like coffee grounds! Though unfocused this shows other blocks of the embedded material which would shine just as brightly if rotated until the light falls across the grain of the material.



The conglomerate, if that it is, formed before some cracking that runs in lines through both the dark blocks of material and the surrounding substrate. Some of that cracking, with the 30X scope, seem to be very thin layers of quartz. A very odd stone.

Skipjack Joe - 4-22-2014 at 11:15 PM

I'm looking forward to hear the answer to your question.

This year I collected some cool white rocks which look like marble. Brought a few home and will add pictures of them to this thread. I don't know what they are either.

Whale-ista - 4-23-2014 at 12:27 AM

Interesting looking.

It would be helpful to know exactly where you found this.

Near the coast? Looks rounded, as if tumbled against other rocks. Could have washed down from higher elevation.

Composition could be quartz monzonite embedded with large feldspar or pyrite crystals.

vgabndo - 4-23-2014 at 10:53 AM

Quote:
Originally posted by Whale-ista
Interesting looking.

It would be helpful to know exactly where you found this.

Near the coast? Looks rounded, as if tumbled against other rocks. Could have washed down from higher elevation.

Composition could be quartz monzonite embedded with large feldspar or pyrite crystals.


Yes, clearly water-worn. Found within half a kilometer of the ocean in some pretty heavily "stirred" alluvium. Given the amount of sea bottom material in this mix, it wouldn't surprise me if the piece was worn in sea water. The square nature of the embedded material does suggest Pyrite.

Marinero - 4-23-2014 at 08:53 PM

Interesting rock. Looks water worn, but later weather eroded. Mineral content is beyond me, but the various minerals look to be eroded differentially, which may be a clue. My WAG is a conglomerate of some sort.

Skipjack Joe - 4-23-2014 at 11:05 PM

I don't think that's conglomerate rock, Perry. Conglomerate is sedimentary rock where the components have been fused together due to compression from weight of the water column and above sediments.

Your rock looks as though the fusion occurred somehow differently. So I did a bit of research and came up with breccia.

http://en.wikipedia.org/wiki/Breccia

Apparently there are different types of breccia, formed in different ways, including sedimentary. Given the nature of baja it's likely due to fault, tectonic, or volcanic.

I've seen these types of rocks in death valley as well ... I think.

Skipjack Joe - 4-23-2014 at 11:18 PM

Actually, I don't think it's breccia either. Conglomerates and Breccias are individual rocks cemented by mineral material. In your pictures I don't see actual individual rocks but a rock that is a composite of several minerals that somehow got combined.

My new guess is that it's metamorphic rock of some sort that's been rounded by water.

[Edited on 4-24-2014 by Skipjack Joe]

David K - 4-23-2014 at 11:58 PM

Maybe it's dinosaur egg painted for Easter?

volcano - 4-24-2014 at 06:12 AM

schist in granite?

bajalearner - 4-24-2014 at 07:32 AM

Quote:
Originally posted by David K
Maybe it's dinosaur egg painted for Easter?


Impossible. Dinosaurs lived before Jesus Christ so they would not have celebrated Easter.

Osprey - 4-24-2014 at 07:38 AM

I wouldn't take it for granite.

Skipjack Joe - 4-24-2014 at 08:08 AM

Quote:
Originally posted by Osprey

I wouldn't take it for granite.



Looks just marbleous.

:rolleyes:

Mexitron - 4-24-2014 at 10:10 AM

Gneiss one Skipjack.

vgabndo - 4-24-2014 at 10:17 AM

Are you guys stoned?

David K - 4-24-2014 at 10:18 AM

Quote:
Originally posted by bajalearner
Quote:
Originally posted by David K
Maybe it's dinosaur egg painted for Easter?


Impossible. Dinosaurs lived before Jesus Christ so they would not have celebrated Easter.


I didn't mean the dinosaurs painted it... it could have been found millions of years later, then painted? :yes:

Mexitron - 4-24-2014 at 10:27 AM

Quote:
Originally posted by vgabndo
Are you guys stoned?


Maybe, but who gives a schist?

Osprey - 4-24-2014 at 10:39 AM

That's a boulder statement than I expected.

Skipjack Joe - 4-24-2014 at 10:50 AM

Do you find the source of the rock confusing?

It's really very sedimentary, my dear Watson, sedimentary.

[Edited on 4-24-2014 by Skipjack Joe]

Skipjack Joe - 4-24-2014 at 11:26 AM

I horde these rocks. Don't know what they are but to me they're beautiful.

baja_rock.jpg - 45kB

Whale-ista - 4-24-2014 at 11:51 AM

Quote:
Originally posted by Skipjack Joe
I horde these rocks. Don't know what they are but to me they're beautiful.


Lovely! Nice looking piece of quartz.
Where did you find it? The location and surrounding landscape tells a lot.

The reddish, weathered boulders around Cataviņa are a form of granite known as
quartz monzonite. It's part of the uplifted batholith that extends all along the San Andreas fault, from Central Baja up to Joshua Tree.

There will be variations, depending on innumerable environmental/weather/exposure factors, but the basic characteristics and appearance are similar- and makes for great bouldering/rock climbing!

(I used to travel these areas with a geologist)

Science doesn't take the beauty/mystery out of a fondness for nature. If anything, I appreciate what I see around me even more after learning about the natural history of the places I visit.

BajaBlanca - 4-24-2014 at 12:21 PM

What a delightful thread.

Mexitron - 4-24-2014 at 12:35 PM

Quote:
Originally posted by BajaBlanca
What a delightful thread.


Yes it has a certain serpentine train of thought....;D

Skipjack Joe - 4-24-2014 at 12:50 PM

Quote:
Originally posted by Mexitron
Quote:
Originally posted by BajaBlanca
What a delightful thread.


Yes it has a certain serpentine train of thought....;D


How about serpentrine of thought?

Skipjack Joe - 4-24-2014 at 12:58 PM

Quote:
Originally posted by Whale-ista
Quote:
Originally posted by Skipjack Joe
I horde these rocks. Don't know what they are but to me they're beautiful.


Lovely! Nice looking piece of quartz.
Where did you find it? The location and surrounding landscape tells a lot.



This off the road to calamajue this time.

It's always proceeds in the same manner. You get out of the vehicle to pick up a rock. Then as you move further you find one that's better and you replace the old one in your pocket with a new one. This continues as your pockets fill up. Eventually you find one that's too big to fit into any pocket so you carry it in your hand. Meanwhile your partner is impatiently honking on your horn to get back to the car. Eventually the small rocks end up in the glove compartment and the large ones roll between the seats during the trip. Months later they end up in a basket in your bedroom, a basket you look at wistfully now and then and remember your last baja trip.

DavidE - 4-24-2014 at 01:06 PM

Nary a clue but that's an interesting specimen.

Way back on the northwest side of Las Tres Vigenes is a deposit of red obsidian.

daveB - 4-24-2014 at 03:33 PM

I wouldn't take it for granite either, or it could be a leverite. But I can see the diamonds.

Whale-ista - 4-24-2014 at 03:48 PM

I try to limit my collecting to 1 or 2 nice/unusual objects per location, per trip. And I prefer the coastline to inland, at least when whales are around.

Not too many rocks in the lagoons, but I find other "treasures"- sea-polished glass for example.

The volcanic areas would definitely have more interesting finds!

bajalearner - 4-24-2014 at 04:40 PM

Quote:
Originally posted by David K
Quote:
Originally posted by bajalearner
Quote:
Originally posted by David K
Maybe it's dinosaur egg painted for Easter?


Impossible. Dinosaurs lived before Jesus Christ so they would not have celebrated Easter.


I didn't mean the dinosaurs painted it... it could have been found millions of years later, then painted? :yes:


Did you really think you had to clerify that or are you throwing eggs at me?

woody with a view - 4-24-2014 at 04:47 PM

it looks sedentary, if you axe me!

grace59 - 4-24-2014 at 04:59 PM

Boy, this is a Tuff one! Of Quartz, someone here knows must know the name of this rock! If you do, Pumice us that you'll post the answer! :lol::lol::lol: This is fun!!

Osprey - 4-24-2014 at 06:15 PM

Can't be conglomerate. That's a prison basketball team.

woody with a view - 4-24-2014 at 07:45 PM

my cat said it's Agate.....

Geo_Skip - 4-25-2014 at 05:52 PM

Don't be silly. No geologist can give you an accurate interpretation from a few photos. Geologists are trained to identify rocks by licking them. (BA, MS Geology)

Geologists rock

durrelllrobert - 4-25-2014 at 06:22 PM

Quote:
Originally posted by Geo_Skip
Don't be silly. No geologist can give you an accurate interpretation from a few photos. Geologists are trained to identify rocks by licking them. (BA, MS Geology)


Taco de Baja - 4-26-2014 at 11:04 AM

It's sometime tuff to ID rocks from pictures...

But this looks like a rhyolitic ignimbrite to me. Also known as a welded tuff, or solidified volcanic ash, or maybe even solidified rhyolitic breccia, as there are a lot of rock chunks in it.

Depending on the heat and the weight, the ash and chunks of rock from the volcano will be welded, or fused, into a solid rock. The more heat and weight the more tightly fused and less porous it will be. Sometimes it will be so hot the chunks of rock will be slightly metamorphosed, as evidenced by the lighter rings around the darker rock chunks in your sample. Generally the closer to the volcano, the more welded it will be, as distance will cool the ash as it falls.

This rock also rolled down a stream as a cobble, resulting in its current rounded appearance.

bajabuddha - 4-26-2014 at 12:39 PM

my guess is that it is metamorphic with the quartzite cross-bedding.

On the other hand, it could be an Indian Love Stone (just another F-R)

dtbushpilot - 4-26-2014 at 03:59 PM

Quote:
Originally posted by bajabuddha
my guess is that it is metamorphic with the quartzite cross-bedding.

On the other hand, it could be an Indian Love Stone (just another F-R)



I'm going with sex stone.

bajalearner - 4-26-2014 at 08:31 PM

Whatever it is, it rocks.

Whale-ista - 4-26-2014 at 10:46 PM

Quote:
Originally posted by bajalearner
Whatever it is, it rocks.


and given it's smooth, round shape, it has also rolled...