Beach pebbles/rocks

[strezman]

This is turning into a science class really fast lol. Probably the most vague description but, any idea about smooth blueish very solid seeming rocks?? I'm sure a pic would be easier but I can't make it to the beach today

[Coasting]

Elementary school science!!!!
Drip some vinegar on it, does it fizz?


http://www.minsocam.org/msa/collecto...d/rock_key.htm

Most of the rocks we find around here in riverbeds are a pretty safe bet

[GoFish]

What are you planning on using these rocks for btw? Been there done that with beach rocks. Are you wanting more biological filtration? Or wanna use them as a substrate in your display?

[WarDog]

Blueish and smooth is probably sedimentary. Not an ideal choice. Neither is metamorphic, can contain metals. Best bet is rock forged from 'liquid hot magma' (Dr.Evil voice), which is Igneous.