BajaNomad

Anyone know about these Green Rocks?

advpulse - 12-19-2013 at 10:10 AM

We were riding motorcycles through Baja Sur a few weeks ago, just north of La Paz along the coast. We came across a section of road where all the rocks were dark green. I have never seen green rocks like that before. Does anyone know what could create green rocks? Is it some type of metal in the rocks getting oxidized? Here is a picture...

http://www.pinterest.com/pin/451485931365565877/

24baja - 12-19-2013 at 10:12 AM

Quote:
Originally posted by advpulse
We were riding motorcycles through Baja Sur a few weeks ago, just north of La Paz along the coast. We came across a section of road where all the rocks were dark green. I have never seen green rocks like that before. Does anyone know what could create green rocks? Is it some type of metal in the rocks getting oxidized? Here is a picture...

http://www.pinterest.com/pin/451485931365565877/


I would say rich in copper.

BajaParrothead - 12-19-2013 at 10:27 AM

My first thought would be copper, but I know nothing about geology.

geomike - 12-19-2013 at 10:50 AM

That's a great photo. I've never walked the rocks in the La Paz area, that said, from your photo it looks like a marine succession laid down near shore. One really good indicator mineral that we find in these areas is a clay like mineral called Glauconite. Here is a link to some more information.

Wikipedia Glauconite

Pompano - 12-19-2013 at 10:52 AM

I don't know for sure, but it may be from the mineral, 'Apatite'. I think you may have been fairly close to the old San Jaun de la Costa mining operations.

I camped near the shore in that same area long ago with some friends from Mulege...and enjoyed it very much. Even found a puppy to adopt...now happily relocated in Utah.

Anyway, apatite is a greenish phosphate mineral commonly used in making fertilizers, among other things.

[Edited on 12-19-2013 by Pompano]

advpulse - 12-19-2013 at 02:46 PM

Here's a link of where we were roughly on the map. We camped at Punto Mechudo beach the night before and traveled to La Paz. The green rocks were unreal. It looked like they had been spray painted but they were everywhere. It did have the same color as fertilizer so maybe it was apatite.

Thanks!

Mexitron - 12-19-2013 at 03:00 PM

Sounds like apatite is more of a crystalline/gemstone type mineral after reading a little. The glauconite might make more since since it is commonly found in environments like this continental shelf marine environment...but hey I'm no geologist, just a dude with a big apatite for knowledge. :bounce:

David K - 12-19-2013 at 03:08 PM

Quote:
Originally posted by advpulse
Here's a link of where we were roughly on the map. We camped at Punto Mechudo beach the night before and traveled to La Paz. The green rocks were unreal. It looked like they had been spray painted but they were everywhere. It did have the same color as fertilizer so maybe it was apatite.

Thanks!


Map link?

Here is the area...




Skipjack Joe - 12-19-2013 at 04:42 PM

Serpentine rock is green like that. We have lots of it around here and the sierra foothills. It's a metamorphic rock, however, and that looks like a sedimentary layer.

bajagrouper - 12-19-2013 at 04:49 PM

Now I know where the Mayans got their Jade.........

danaeb - 12-19-2013 at 05:16 PM

The beach after El Cajete and just before the road takes off up the hill to the mine is littered with green rocks - I have a collection of them. When you look at the cliffs above the beach, the green sedimentary layers are clearly visible.

advpulse - 12-19-2013 at 07:13 PM

Sorry about the link. Somehow I thought I pasted it. Here is roughly the location we were. Just coming down from the hills when the road meets the beach on the way south to La Paz.
https://goo.gl/maps/lQcwh

geomike - 12-20-2013 at 11:00 AM

My wife says I never admit when I'm wrong...well in this case clearly I was mistaken.

Once I re-read Pompano's reply and saw the map I remembered I was there at the San Juan de la Costa Mine. Was waiting for the Norra Baja Mil in 2011 I think. At the time I had no idea what the mine was producing ( I know, for a Geologist not to have done the homework on the area he was going to see is unforgivable.. I feel shame )

So the answer is Phosphorite. I got the mineral wrong but the environment of deposition was correct. Here is a link to a google book on the subject.
San Juan de la Costa Phosphates

mtgoat666 - 12-20-2013 at 11:27 AM

Quote:
Originally posted by geomike
My wife says I never admit when I'm wrong...well in this case clearly I was mistaken.

So the answer is Phosphorite.


i think the OP posted a photo of tuffs interbedded with fluvial or marine sediments, and i throw out a SWAG that the green is a zeolite or a some oxidization or chemical weathering byproduct.

the OP should go back and get close up pictures and place a beer bottle in the picture to show scale (no tecate, only pacifico will do)