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Hot Topic (More than 10 Replies) Wake County; Ultramafic Bodies (Read 10806 times)
JoeM
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Wake County; Ultramafic Bodies
Mar 4th, 2014 at 1:01am
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The Ultramafic Bodies of Northern Wake County offer some great rockhounding.
These areas are usually known and typified by their soapstone outcrops,
which are usually sopastone or many varieties of a talc-chlorite-schist mix.
When the water level is down Barton Creek at Falls Lake is a great place
to view the ultramafic geology, but being part of the State Park,
collecting is not allowed. Still a great place to train your eye.

As John Parker points out it in his 1979 report, "Geology and Mineral Resources of Wake County",page22,
  "A swarm of dark intrusive rocks...occupies a considerable
area in north-central Wake County and adjacent parts of Granville County.
They are scattered chiefly over a belt 5-6 miles wide that lies east of NC Hwy 50
and north of Six Forks in the belt of mica and horneblende gneisses."

Besides for the soapstone, serpentines, epidote, chlorite, actinolite, kyanite,
and other minerals to be found in these rocks,
one of the most interesting to me is what is called "Chromite Ore".
Here is more from John Parker's report;
"Most of the ultramafic bodies seem to consist chiefly of massive to poorly foliated soapstone.
Talc commonly composes half or more of this rock, mixed with chlorite and smaller amounts of actinolite.
Carbonates and opaque minerals are common. Actinolite in some rock forms slender prisims
2 or 3 inches in long embedded in talc and chlorite. In places, smaller actinolite crystals form rosettes.
A little ruby corundum has been found in the body that crosses SR 1842 north of Pleasant Union Church."

And that is exactly where this piece of Chromite Ore came from.
The first pic is of two large pieces. The rosettes, or sprays,
on these pieces are schorl.


  

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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #1 - Mar 4th, 2014 at 1:09am
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We were told many moons ago that the bright emerald green mineral
on and in the rock was "crystalline Chromite", but now I question that.
Parker mentions a "fuchsite coating", and I'm wondering about Theophrasite?

  

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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #2 - Mar 4th, 2014 at 1:19am
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Parker says this about the chromite ore from Pleasant Union Church Road,
" The massive chromite rock here includes olivine, tourmaline,
veins of cross-fiber talc and chrysotile, with coatings of Thulite and Fuchsite."

Here's a cut surface,
  

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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #3 - Mar 4th, 2014 at 1:23am
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We'll have to get some better pictures of these, but here's what
all the rockhounds want from this spot, the Rubies! Cheesy
  

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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #4 - Mar 4th, 2014 at 7:48pm
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We'll get back to more pics of the rubies later.... Smiley
Here are a few pics of other specimens from Northern Wake County.

We'll start with the Soapstone, or Talc.
This is your average white-grayish variety, but, as stated, you can find
all grades of mixtures with more green, red, etc.
And a lot of it makes for very good carving material.
  

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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #5 - Mar 4th, 2014 at 7:50pm
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Here is a piece of the Actinolite and a piece of the
Chlorite-Talc-Mica-Schist mixture.
« Last Edit: May 7th, 2016 at 10:38pm by JoeM »  

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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #6 - Mar 4th, 2014 at 7:55pm
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I have better specimens but can't put my hands on them right now.
Here is a piece of what looks like silicified talc with actinolite.
And a large piece showing the Actinolite rosettes.
  

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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #7 - May 7th, 2016 at 10:47pm
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I'm going to have to look at those "rosettes" pictured above again and make sure they aren't schorl.
Speaking of schorl, here's a couple pics of some we found in a lens of the chlorite talc at a new development
in the ultramafic area recently. This green matrix is more like sand than talc?
And these pieces have soaked in oxalic for several days.
  

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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #8 - May 7th, 2016 at 11:02pm
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Recent talk about chlorite mica schist got me to looking at the talc and schist around here.
Here are pics of some of the chlorite-mica talc, soapstone, from the Barton Creek area.
I never get tired of looking at all the different mixtures this stuff comes in.
So my life isn't that exciting.  Huh
I took the front piece in the first pic and ground down one corner
and show it dry, pic 2, and wet,pic 3. Then I carved something out of real quick. Wink
  

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Re: Wake County; Ultramafic Bodies
Reply #9 - May 7th, 2016 at 11:29pm
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Thanks for all of the great info and photos Joe. Hope to get out there and dig with you soon buddy!
  
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Re: Wake County; Ultramafic Bodies
Reply #10 - May 8th, 2016 at 10:59am
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A agree 100%  Thanks for all the great information and photos, that's all fascinating, and even more so since it's all so close.  Wake County has some pretty cool stuff!
  
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JoeM
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Re: Wake County; Ultramafic Bodies
Reply #11 - May 8th, 2016 at 11:19pm
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oh yes, and the ultramafic bodies of northern Wake are well delineated on the geologic map of the county. Wink

Another thing very hard to discern from all the other local rock because the exterior of all the rocks look the same,
so you really need a fresh break to spot it, but there's veins of serpentine and possibly, antigorite or vesuvianite, sandwiched in with the country rock.
Most of the time it's a pencil thin stringer running thru some huge boulder and impossible to retrieve.
But it's something to keep an eye out for.
I would probably call this stuff jade if it weren't so soft. Mohs 3 so it would be good carving material.
First pic is dry so you can see how you can't tell much looking at the weathered exterior,
and the rest are wet.
Happy Hunting!

  

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