[Rockhounds] What is this rock?
Dora Smith
tiggernut24 at yahoo.com
Wed Nov 12 06:35:16 PST 2008
Well, if the reaction of dolomite with acid is weak, then I guess this rock
reacts weakly indeed. I seem to recall from my Great Austin Limestone
Survey that dolomite reacts pretty definitively with HCl.
I thought that rock eitehr reacted or did not, and if like alot of rock
around here it was mixed with clay than it might have trouble fizzing it up.
Actually some parts of the rock fizz on contact with HCl and some don't,
which is kind of odd. Not violent fizzing; it just turns white and there's
a slight distinct fizz. Fizzes atleast as hard as limestone clay rock
from creek bottoms does, though.
Yours,
Dora Smith
Austin, TX
tiggernut24 at yahoo.com
----- Original Message -----
From: <Pmodreski at aol.com>
To: <rockhounds at lists.drizzle.com>
Sent: Tuesday, November 11, 2008 11:54 PM
Subject: Re: [Rockhounds] What is this rock?
> I'll agree too, they certainly look like gneiss.
>
> Some gneisses can contain calcite; the rock can be intermediate in
> composition between a marble and a silicate gneiss. And yes, it's
> certainly true that
> dolomite would react weakly with acid. And a regular gneiss (made of
> quartz, feldspar, etc.) would not be scratched by a knife. It sounds
> like your
> rock is perhaps as I say, a banded, gneissic marble; or one could say, a
> calcareous gneiss--such things exist, it might not be unreasonable to
> find them
> somewhere in the Adirondacks.
>
> I just did a little Googling on this (Adirondack marble), and yes, there
> are
> indeed lots of marbles in the Adirondacks. There are even the
> "Adirondack
> Marble Caves"! And graphite occurs in some of these marbles, so some of
> the
> dark grains in your rocks may be graphite. I would now say your rocks
> are
> probably a gneissic, impure marble. Which means, as a marble, it would
> have a
> slight, slow solubility in water and a very slight tendency to dissolve
> in
> your fish tanks, but probably very slowly, much slower than your local
> Texas
> limestone would.
>
> Pete Modreski
>
>
> In a message dated 11/11/2008 8:48:12 P.M. Mountain Standard Time,
> codeburner at gmail.com writes:
>
> 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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