Reeling around a Reel Vug.

[arappaho]

Only 69 more days to the next Reel Dig! Can't hardly wait!

Lots of times you look at these clayey-looking clumps in the vugs
and think that's all it is. But if you look a little closer there's no telling
what you might find.
Here's a vug from the Reel.



As noted the blue line represents about 16mm. In the clayey-looking
area you can hopefully see the negative impressions of two large
crystals that have eroded away. I think this makes it an "epimorph".

And what are those black splotches in the lower right area of this vug?



I know you sure can't say for sure from the pic. Sorry, but it's reel small.
Maybe Hematite, but at some angles there's a bluish flash to it
that makes me wonder if it might be something else.
Continuing up that side of the vug I came across this nice little
cluster of quartz crystals.



Note that there are more of those black splotches in the upper
right corner of this pic. Maybe you can see the blue flash.

Moving on around to the other side of the clayey area is what I
thought was reely cool. I was thinking these were either Pyrite or
Siderite on their way to becoming Limonite morphs but Scott has
pointed out to me that they are probably coated Calcites.





one more time.......



And at the bottom of this vug are some reel pretty crystals. Can't
say for sure if they are Citrine or not without giving them a good
bath in Iron Out, but I'm afraid if I do that I might ruin the Calcites.
Love the color, tho.



Sorry the pics aren't better, I'm still working on it.
But thanks for looking and I hope to see y'all REEL soon. ;D

Joe

[Barrett]

A very good thread. Make sure and take note

[tracey]

69 days!!! on my calender.
Spectacularly interesting piece, amazingly clean. It must be amazing to handle, turning over and over to find each new bit of beauty!

[lauriesrocks]

Joe, I think the impressions you have are simply casts of former crystals, not epimorphs. There is a difference. I have heard in the past of siderite having been identified from the Reel. What you have looks like siderite to me. Because of the rhombic form, it could not be pyrite, and the coloring does not look like oxidation due to replacement. The crystals look fresh, solid, and primary. So I would guess siderite. Most rhombic carbonates in the werstern Piedmont area tend to be siderite, though some from Hiddenite has been identified as having very little iron content and thus closer to calcite. Of course, without chemical analysis, positive determination of either siderite, calcite, or ankerite (all posibilities) is only an educated guess.

[arappaho]

Thanks AG, Tracey, and Laurie,

Yes Laurie, I'm not clear on the differences involved between the cast
and the epimorph in this case and will have to do some reading on it.
If you would care to elaborate, feel free, I'm all ears.
And I'm with you on the Siderite. Pyrite is definitely out. The Siderite
reely makes more sense to me, but it's awfully well formed and still
in good shape. Here's an example of the Calcite Scott sent me to look
at; www.mindat.org/photo-160283.html

Like you said, It's pretty hard to say for sure without doing some
tests that would/may destroy it. Let's just call it Ankerite!

Joe

[lauriesrocks]

A cast is a "negative" impression formed by the removal of a crystal from a matrix, leaving a hollow void showing the shape of the original crystal. When you dig a quartz crystal out of a clay pocket, and after removing the crystal. you can see the "mold' left in the clay where the crystal was. This would be an example of a cast. Casts are usually formed by the mechanical or chemical weathering of a crystal from it's matrix. Often, but not always, the enclosing matrix will be harder than the original crystal, so it will be more resistant to weathering and will thus survive longer. Calcite is a common mineral that will chemically dissolve over time, leaving a cast in the surrounding rock. An epimorph is a type of pseudomorph, where one mineral replaces another, usually as a relatively thin layer on the outer surfaces of the crystal, while the inner mass of the crystal is dissolved or weathered away, leaving a hollow space inside, The outside of the crystal will still retain the shape of the original mineral, just as a pseudomrph does, but the inside will be hollow, because the replacement process was not completed. Without the hollow space, it is simply a pseudomorph. Again, calcite is probably the most common mineral to form epimorphs. Epimorphs thus are a "positive" feature showing the actual shape of the original crystal, while a cast is a "negative" feature, essentially a mold, of the original crystal. Does this make sense?

[arappaho]

Yes Laurie, thank-you very much.
I agree there appears to be a cast evident. The thing that throws
me off is the "clay-looking" material. I don't know if I would call it
clay? I'm thinking, probably incorrectly, that it IS the "dissolved"
oxidized remains of whatever crystal left the cast?
It's kind-of like the old question; Which came first, the chicken or
the egg?"
I do not see an outer layer of the absent crystals present, just a cast
in that clay-looking material I'm wondering about so I think I see why
it is not an epimorph. So here's a hypothetical scenario to think about;
What if the two casts were large Siderites, that broke down over
time, forming this clay looking coating, and then reformed in all the
"baby" Siderites we see today on the outside of this coating?
There in lies my confusion.

Thanks, Joe

[ncbbqnut]

Joe,

As usual, great specimen, great photos, and great questions and mystery!

It all reminds me of that animated rockhounding feature by Picks-Are Productions, It's a Vug's Life!

Dennis