[Rockhounds] What is this rock?

[J Bryan Kramer]

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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