Thread: Help I.D. Rocks Please

I'm new here. So, Hello Everyone!

I have some rocks I've had around the house for years and am considering putting some in my aquarium. I would like to know what type some of these are so I can research them and find out if they are safe for freshwater aquariums.

Thanks!

1)



2)



3)



4)


5)

i don't see anything that looks suspicious in that it might kill the fish in your aquarium, but i'd suggest to leave each of them (separately) in a bucket of water (or a cup if they're small pebbles) and see if anything leaches out - observe any possible colour changes and taste the water to see if any salts have dissolved out

Wouldn't hurt to soak them with a bit of acid too, then flush well and soak again in rainwater.

Originally Posted by Pong

Wouldn't hurt to soak them with a bit of acid too, then flush well and soak again in rainwater.

except for item #1 which appears like some sort of limestone to me
in fact, the acid test would only point out the difference between acidic and alkaline rocks, and would have little relevance for their behaviour in an aquarium

what you want to find out is if there's any water soluble components in them that might harm your fish, or affect the pH of the water

as a further aside, rocks (3), (4) and (5) appear to be water-worn - if they come from a river environment then they should be OK
however if they come from a beach then it's probably best to rinse any excess salt off that might be attached to them

1)This is a limestone. One can see a lamellibranch fragment in the first photograph, as well as vugs (solution cavities).
2)This one is interesting. It could be a gneiss or a granodiorite. The flat surface is probably weathered, which accounts for the different colour, but it might just be showing slickensides, the result of fault movement.
3)This one would really benefit from a scale. If it is less than 3" across I think it is a jasper pebble. i.e. amorphous silica. If it is larger then it is a very iron rich siltstone. (Maybe.)
4)The cobble is too well worn to be offer any definitive identificaiton, but I suspect it is an acidic plutonic rock.

I have no idea how these would react in an aquarium. The limestone is the one I would be most concerned about.

Originally Posted by John Galt

1)This is a limestone. One can see a lamellibranch fragment in the first photograph, as well as vugs (solution cavities).

This one almost looks like a chert to me. I'm not good at identifying rocks (yet hopefully), but the conchoidal fracture at the bottom right of the 2nd picture makes me think chert. Also, I have chert that has very similar colors and fractures - which could also mean I actually have a limestone that is very similar... :?

Chert does not contain solution vugs or fossil bivalves.
I would not describe the fracture as conchoidal, but do think it is typical of microcrystaline limestones.
As always, rock identification from photographs is notoriously flaky, so who knows?.

i'm fairly certain (1) is limestone although it could be partly metamorphosed by the looks of it