Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Look in all the landscape, masonry, soils, brick... yards anywhere near you.
Many of the stones are shipped all over the USA, and the more unusual (read high priced) are shipped from all over the world.
The rock yards will call the rock by all sorts of different names.
You simply have to go see what they have. No use making phone calls, and do not ask for any rock by any name known in the aquarium trade.
Sometimes you will get a really knowledgeable person who can tell you some of the alternate names of a rock as it may be known in the landscape trade. You might use that name when calling some other store.
I do not know the geological origins of most of the rocks, but getting a sample to test is a good idea.
If you have traveled a ways and need to know right away you could carry with you some acid such as the API nitrate test. If I remember correctly bottle #1 is acid that is strong enough to react with limestone and related rock.
For rock yards that are closer you could bring some zip lock baggies with you and a Sharpie pen. Look on the ground around the rock and pick up some scraps. Label it with where you got the rock and what they call it. When you return home test with acid, and also put the bits into a jar of water and test GH, KH, pH and TDS after a few days.
The more specialized the store the more expensive the rock will be. A store that sells by the truck load may also sell by the bag or by the pound. A store that only sells by the pound will usually charge more per pound. Highly likely they just went to the same rock yard to get it.