[Rockhounds] What is this rock?

[Tim]

Dolomite can be many colors/shades, with or without patterns or visible
minerals. As someone posted yesterday, white/cream or white with black
crystals is very common. It is very much basic (and therefore reacts with
HCl) since it is used alone or in combination with lime to increase soil pH.


Tim Fisher 
Ore-ROCK-On! 
Email address at http://OreRockOn.com


-----Original Message-----
From: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com] On Behalf Of Dora Smith
Sent: Wednesday, November 12, 2008 6:32 AM
To: J Bryan Kramer; Rockhounds at drizzle.com: A mailing list for rock and gem
collectors
Subject: Re: [Rockhounds] What is this rock?

I don't think so.  As I recall, dolomite is limestone with magnesium in it.
It is found around Austin, and is higher quality than most limestone found
around here, and as I recall it reacts pretty strongly with HCl.   It ahs
been a few years since I did my Great Limestone Survey, and I had to travel
some distance and search to fnid dolomite.

Dolomite is very hard, very fine, and a distinctive tan-yellow color.   This
rock does not have dolomite.

Yours,
Dora Smith
Austin, TX
tiggernut24 at yahoo.com
  ----- Original Message ----- 
  From: J Bryan Kramer 
  To: Dora Smith ; Rockhounds at drizzle.com: A mailing list for rock and gem
collectors 
  Sent: Tuesday, November 11, 2008 9:47 PM
  Subject: Re: [Rockhounds] What is this rock?


  Doesn't dolomite react weakly with acid?

  BK


  On Tue, Nov 11, 2008 at 22:44, Dora Smith <tiggernut24 at yahoo.com> wrote:

    I actually scrubbed them well in dish washer detergent, soaked in
bleach, and boiled before testing them with toilet bowl cleaner.

    What do you make of the fact that they do react with HCl?  And should
gneiss scratch with a knife?

    Yours,
    Dora Smith
    Austin, TX
    tiggernut24 at yahoo.com
    ----- Original Message ----- From: "Carolyn Reynard"
<sunstone3 at hvc.rr.com>
    To: "Dora Smith" <tiggernut24 at yahoo.com>; "Rockhounds at drizzle.com: A
mailing list for rock and gem collectors" <rockhounds at lists.drizzle.com>
    Sent: Tuesday, November 11, 2008 9:43 PM
    Subject: Re: [Rockhounds] What is this rock?



      Dora, Your rocks certainly look like gneiss. The banding of light and
dark
      minerals is typical.  The dark mineral(s)
      would be bioitie or hornblende. The light mineral(s) would be quartz
and/ or
      feldspar.  One would not expect any reaction to HCL. Rinse them well,
they
      probably won't be a problem in a fish tank.

      I'm not familiar with an Adirondack smell. Your Austin smell would
seem to
      be like an earthy moldy clay odor.

      Carolyn Reynard
      Poughkeepsie, NY


      ----- Original Message ----- From: "Dora Smith"
<tiggernut24 at yahoo.com>
      To: <rockhounds at lists.drizzle.com>
      Sent: Tuesday, November 11, 2008 10:05 PM
      Subject: [Rockhounds] What is this rock?


      I asked my sister to bring me home some Adirondack granite from our
family
      home for my fish tank, and she brought me these two rocks.   Photos
are at
      http://good-times.webshots.com/album/568626982hMlTIK

      They look sedimentary; they are banded.  They are heavy and softer
than
      granite ought to be; they scratch with a knife.  They react weakly
with 10%
      hydrochloric acid (toilet bowl cleaner).  Some parts of the rock
definitely
      fizz, especially if the rock is hot, but not as vigorously as
limestone.
      Sometimes acid toilet bowl cleaner leaves behind a rough residue of
large
      sand grains easily scratched off.  They do not fizz with vinegar.

      The rock smells distinctly like Adirondack rock and distinctly NOT
like
      Austin rock.  In Austin nearly all rock is soft limestone, and it
always
      smells yucky.   There is no other way to describe it.   The soil
smells the
      same sort of yucky.

      I thought they were limestone until I saw photos of gneiss; they look
alot
      like gneiss.  but from what I am reading gneiss is not made from
limestone.
      Usually it is made of solid silicate rock that is already hard and
durable.

      Can silicate react with hydrochloric acid?

      What is this rock?

      If it is limestone based, is it hard enough not to throw off the
chemistry
      of my fresh water tropical fish tank?   In Austin the water is hard
when it
      is taken from the river but it is treated with water softeners.

      Yours,
      Dora Smith

      Yours,
      Dora Smith
      Austin, TX
      tiggernut24 at yahoo.com

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  -- 


  "The thunderbolt falls on an inch of ground; but the light of it fills the
horizon."

                         Ralph Waldo Emerson

  J Bryan Krämer
  North Florida, USA
  photos at:
  http://pbase.com/photoburner


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