WrightwoodCalif.com Forum

Public Forums => Outdoors => Topic started by: storm on Jul 23, 07, 11:25:57 AM

Title: Beautiful Spessartine Garnet Schist...
Post by: storm on Jul 23, 07, 11:25:57 AM

Found this earlier today:

(http://img.photobucket.com/albums/v190/stormbythesea/Rock%20Collection/ColorfulSpessartineSchist3.jpg)

(http://img.photobucket.com/albums/v190/stormbythesea/Rock%20Collection/ColorfulSpessartineSchist2.jpg)

(http://img.photobucket.com/albums/v190/stormbythesea/Rock%20Collection/ColorfulSpessartineSchist1.jpg)

Title: Re: Beautiful Spessartine Garnet Schist...
Post by: Janie on Jul 23, 07, 02:12:02 PM

I'm curious as to why you are calling this a schist when it is foliated like gneiss and/or stretched like mylonite? I would like to know how to tell the difference.

Title: Re: Beautiful Spessartine Garnet Schist...
Post by: storm on Jul 23, 07, 07:26:23 PM

I'm curious too.   ;)

I really don't know what to call this type of formation.  But I've posted these photos on a Geology Forum and hope they can give me some insight.  I'm hesitant to call it a gneiss because of the yellow bands (likely Spessartine--I've had similar yellow material tested by a lab).  It does remind me of the banded quartzite we have around here--here's a photo of the Spessartine Garnet:
(http://img.photobucket.com/albums/v190/stormbythesea/Rock%20Collection/SpessartineGarnet16.jpg)

Here's pink Rhodonite with clear-ish Quartz, black Manganese Oxide and yellowish Spessartine:
(http://img.photobucket.com/albums/v190/stormbythesea/Rock%20Collection/Rhodonite17.jpg)

Here's pink Rhodonite bands in Quartzite:
(http://img.photobucket.com/albums/v190/stormbythesea/Rock%20Collection/RhodoniteinQuartzite.jpg)

All of these have been identified by Cannon Microprobe Laboratory in Seattle.

I found a reference to Spessartine occurring in Gneiss:

"Hawley Formation (carbonaceous schist facies) (Middle Ordovician)
Gray, rusty-weathering, fine- to medium-grained, generally layered schist and granofels, composed of quartz, oligoclase, and biotite; some muscovite and graphite, rare garnet and kyanite or sillimanite. Layers of quartz-spessartine rock (coticule) common."

We have nearly all of those minerals around WW...

Title: Re: Beautiful Spessartine Garnet Schist...
Post by: storm on Jul 23, 07, 07:35:53 PM

I think this rock meets the definition of gneissic on Wikipedia.

Man, I could spend all week on the Internet looking up things related to our local rocks and minerals (and still not really understand anything...).

Title: Re: Beautiful Spessartine Garnet Schist...
Post by: storm on Jul 23, 07, 07:49:54 PM

I did find this photo of pink Spessartine with Magnetite blasts (specks) on the same site as the Forum I post questions on:

http://www.mindat.org/photo-38883.html (http://www.mindat.org/photo-38883.html)

Title: Re: Beautiful Spessartine Garnet Schist...
Post by: storm on Jul 26, 07, 02:07:48 AM

Some geologists have suggested to me that they consider these specimens to be gneiss...