(I couldn't figure out what forum to post this in.) I collect mineralogically interesting beach rocks from a geologically-complex area around Boston (Marblehead). Some look to me like they're displaying flow banding; some, magmatic immiscibility. Some have ~micro-graphic granite~. (the graphic texture is (almost) too small to see w/ the naked eye) Some have almost agate-like bands w/ xls on one side, all swirling around (folded?). And so on. I haven't figured out even where to look for information about these / this kind of rocks. My first question was: What minerals would this ~magma~ have turned into if it had cooled slowly enough? Now I just want to learn enough to be able to look at one of these rocks and read its story, tell how it formed. (I'm not a geologist; just love geology, mineralogy, etc.) (MIT: Pure Math, Computer Science) I'd treasure advice on where all to look, what discipline(s) this might fit into, technical terms that would help in searches, etc. http://www.mindat.org/forum.php?read,11,253515,253515#msg-253515 Wed, 19 Jun 2013 00:00:57 +0000 Phorum 5.2.15a http://www.mindat.org/forum.php?read,11,253515,253749#msg-253749 http://www.mindat.org/forum.php?read,11,253515,253749#msg-253749
The first one looks like almandines in some kind of shist,
Third one is some variety of chalcedony, probably flint
Second... I am not quite sure. For sure it is sedimentary rock, I see a lot of calcite, I think it has grains, so maybe it is sandstone, or even limestone with grains.]]> Piotr Zając Identity Help Tue, 28 Feb 2012 23:47:09 +0000 http://www.mindat.org/forum.php?read,11,253515,253733#msg-253733 http://www.mindat.org/forum.php?read,11,253515,253733#msg-253733
I was definitely remiss in not including any photos!

Here's one of each rock that I have out for this purpose. I can certainly make zooms if they'd help.]]> P. Michael Hutchins Identity Help Tue, 28 Feb 2012 20:58:30 +0000 http://www.mindat.org/forum.php?read,11,253515,253646#msg-253646 http://www.mindat.org/forum.php?read,11,253515,253646#msg-253646
[www.bostongeology.com]

Vik]]> Vik Vanrusselt Identity Help Tue, 28 Feb 2012 00:02:34 +0000 http://www.mindat.org/forum.php?read,11,253515,253521#msg-253521 http://www.mindat.org/forum.php?read,11,253515,253521#msg-253521 Paul Brandes Identity Help Sun, 26 Feb 2012 22:23:17 +0000 http://www.mindat.org/forum.php?read,11,253515,253515#msg-253515 http://www.mindat.org/forum.php?read,11,253515,253515#msg-253515
I collect mineralogically interesting beach rocks from a geologically-complex area around Boston (Marblehead). Some look to me like they're displaying flow banding; some, magmatic immiscibility. Some have ~micro-graphic granite~.
(the graphic texture is (almost) too small to see w/ the naked eye)

Some have almost agate-like bands w/ xls on one side, all swirling around (folded?).

And so on.

I haven't figured out even where to look for information about these / this kind of rocks.

My first question was:

What minerals would this ~magma~ have turned into if it had cooled slowly enough?

Now I just want to learn enough to be able to look at one of these rocks and read its story, tell how it formed.

(I'm not a geologist; just love geology, mineralogy, etc.)
(MIT: Pure Math, Computer Science)

I'd treasure advice on where all to look, what discipline(s) this might fit into, technical terms that would help in searches, etc.]]> P. Michael Hutchins Identity Help Sun, 26 Feb 2012 20:40:12 +0000