geology, rocks, and arils (was Re: Region 7 potluck & arilbreds

In a message dated 97-02-23 20:41:58 EST, you write:

>I'm interested in growing a few arils/arilbreds myself.  Would they do
>well in my part of Zone 7 (on the border of Zone 6)?  I also have a lot
>of bits of rock just a few inches down in my soil - I think it's shale
>maybe - is shale anything like chert?
>Kim Diamondidis
>Germantown, Maryland

I can't comment on your climate, but when they say chert beds, they mean rock
piles.  I would say at least 50% rock fragments (up to 80%), with the
fragments ranging from 8 inch rocks to almost sand grain size.  If I put a
shovel of my garden 'soil' through a screen with 1/4 inch openings, more than
half won't go through in most places.

I was hoping somebody who knows about geology would answer your question but
I will take a stab at it - keep in mind I don't much know what I am talking
about on this one.  Shale is usually a soft rock composed of sedimentary clay
or silt that has been compressed into a semi-hard state but not metomorphized
(is that a word?) by high enough temperature and pressure to turn into 'real'
rock.  If it is at the soil surface, it will weather fairly rapidly into clay
or silt.  Chert is a silica based hard rock that comes from ..... I don't
know what.  It's what's left when softer, more readily weathered stuff is
weathered to clay.  So I suspect shale would not provide the kind of 'sharp'
drainage that chert does.

Linda Mann lmann76543@aol.com east Tennessee USA
apologies to geologists
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