[ RadSafe ] Radon travel in granite

Dan W McCarn hotgreenchile at gmail.com
Mon Jul 28 03:08:10 CDT 2008

Hi Al:

I appreciate your remarks.  I was using some numbers for hydrologic
conductivity / permeability in unfractured granites that were quite low.

I'll convert pCi/g to ppm tomorrow, that I can do easily. Typical Wyoming
granites are 10 ppm which when weathered, provide enough U to make deposits.
Anatectic granites such as in Namibia run up to 100 ppm, but are not found
here in the States and are mineable as ore deposits for U.

I would think that it would be quite unusual to find a granite body with an
average of 50 ppm.  That may be possible if there are intrabatholithic
veins, but outside of veinlets or locally enriched granites, I would believe
10 ppm would be "normal".

But then marine shales are also high, such as the Chattanooga shale with
about 100 ppm U.  It's not mineable because extraction from the organic
matrix is almost impossible.

I was looking for U238 in your report, and it was missing.  Was that an

Dan ii

Dan W. McCarn, Geologist; 3118 Pebble Lake Drive; Sugar Land, TX 77479; USA 
HotGreenChile at gmail.com   UConcentrate at gmail.com

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf
Of al gerhart
Sent: Saturday, July 26, 2008 4:30 PM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Radon travel in granite

Hi all,
  First post, long time lurker.   Finally something I can contribute to,
some facts on radioisotope content, countertop size, porosity of granite,
and Radon/radiation levels.
  Countertop granite is pretty porous.   We cut and polish wet, it soaks up
the water, turns darker.  Water will soak through the center of the slab in
a few hours.
  We have to use a torch to dry out places that need epoxy, seams, rodding
grooves, lamination edges.   It takes a while to dry it out, heat and let
cool, heat again, and so on.
  There has been an explosion of newer stones that were less likely to be
used years ago, but these days they resin the back, apply fiberglass mesh,
so it doesn't break up during polishing.  Some stones get a coat of
polyester resin, which is then ground off during polishing.  The resined
slabs still soak up the water anyway, and they stain from oil or even hard
water, so there is still some amount of porosity present.
  As to emanation rates, I know several leading Radon techs and a few Radon
scientists (Kitto and Steck).   The Radon emission range will run from 4
pCi/SF/Hr to over 500 pCi/SF/Hr (that would be Niagara Gold, it was featured
in both the NY Times story and the CBS Morning show).  The Niagara Gold
sample was from my sample collection, part of a 72"  x 18" remnant that I
bought off a competitor here in Oklahoma.  
  That particular sample measured over 200 uR/hr Gamma (PM 1703 on contact,
yes, I need a better meter) but the hottest spot on that remnant was  as
high as 250 uR/hr Gamma, or 5300 to 6300 cpm with one of George's LENi
Geiger counters (pancake probe, about 9 mm standoff).  10.5 mR/Hr
  As to 50 ppm being reasonable, not sure, we aren't smart enough to convert
ppm into pCi/g or cpm.  :)   I can say that I have seen reports much higher,
200 to 4,000 cpm.
  I have a lab report on the countertop in Houston Texas that lead to this
flurry of reports.  It gave two Radium isotope contents as 1,130 pCi/g  or
  Potassium 40, 53.9 .
Scandium 46 , 31.65
Cobalt 60 , .13
Cesium137 , .189
Thallium 208, 37.8
Lead 210 , 415.5
Bismuth 212 , 85.46
Bismuth 214 , 410.77
Lead 214, 484.99
Radium 226 , 986.95
Radium 228 , 128.34
Thorium 228 , 144.76
Uranium 235 , 37.83
  ARS Houston Granite Countertop report
  We use US units here, darn it, but I'll figure out how to convert the
example in Kai's example.
  Can anyone tell me if it is possible to convert a Geiger counter reading
into PPM of Isotopes?  Sure it must have a lot to do with the isotope rad
level, but are there any rules of thumbs for a quick and dirty guess?
  Thanks for the excellent site.  I am learning so much here.
  Al Gerhart
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