Is This Lace Rock? Rock Id Help Please!

[the420buzz]

When I moved into the house I'm in now, we found a box in the back shed with some plastic plants in it, along with these rocks. At the time, I didn't have a use for the rocks and I didn't think they'd be the greatest for my SA cichlids and I figured they'd raise the PH. I did use the plants however (score )

But now that I'm turning my 60 gal into an african tank (tanganyika specifically), I was thinking about buying some lace rock, and then I remembered that I had these out in the shed. Now, I'm no rock expert, so I'm not positive that these are lace rock, but I think they may be. I've taken some pictures and I hope that you guys could tell me whether or not its lace rock, and/or if its not, will it be suitable for a tanganyikan tank? Thanks to all ahead of time.

(NOTE: Sorry for the amount of pictures too)

(a shot of all the rocks)

(rubble in bucket)

(and some macro-mode shots for detail to hopefully help)

Thanks ahead of time to all for attempting

 

[walkers101]

i would take a guess that they are

 

[drobbyb]

It could be lace rock, but with the seashells it leads me to believe that it is actually some type of rock from the base of a coral reef. Not to worry though, it will do the same thing to your water as lace rock will, it will raise your pH and hardness.