Hello konrad...

Like an old fire house type bricks? Are they smooth or kinda chunky (still kinda smooth but with small chunks as opposed to SUPER smooth)?

I use both to keep the grass back from my peach trees and no bad news yet. They have been in the ground for six months now. The grass does have a tendency to grow in between them but not bad at all.

Thanks,...these are solid, one side smooth, the outer side kind of wavy rough, or you might call it chunky?

Dont quote me on it but I think they should be OK.

They are a pain in the butt to place in the dirt though. I bury mine at least half way down to keep grass at bay. An area of 4' x 4' took me half a day. But I like to take breaks:-) I place them at least 2' from the tree

Konrad, I'm going to guess that those aren't dyes, but pigments, and they have to be pretty stable in order to not fade and bleed in use.

And if they are inclined to bleed, well, they've had a few years to get it out of their systems, if they are used or have been exposed.

I'd probably use them.

Konrad,

Bricks are not dyed. A pigment is added to make bricks yellow or black or whatever. Red bricks are naturally red due to the iron in the clay. They are fired in a kiln at like 1500 degrees.....no worries.

I think Konrad's bricks might not be vitreous in nature because he specifically mentioned that they look like they are made of concrete.

We have clay bricks here that were made quite a while ago but they weren't fired at high enough temperatures to render them stable against freeze/thaw cycles; they crumble if exposed and were not used as fascia unless painted. Ground contact destroys them in a season.

Concrete pavers are pretty tough and if that's what he has they should hold up.

Thank you all!
I didn't explain myself clearly,...should have said blocks, yes, the real brick are fired, these look like made from concrete, Mark and others are on the right track, saying pigments, [my coworker said dye] not sure what pigments are, I'm pretty sure they have to be stable not to fade in the sun and leach in rain.
I guess these are used now these day's more then the "real" brick, being cheaper to produce, or can take the load of structure better then real brick? You see them allot on commercial buildings on the base, about 2 to 4 feet up.
Any insight in what pigments are made of?

Konrad,

There are both natural and synthetic pigments some are toxic and some are not. There is no way to know what the coloring agent is in them without asking the manufacturer. Way back when for example charcoal was used to make black, non toxic.....white came from lead treated with vinegar.....so some would consider that toxic. In our modern world there are many coloring agents available so if you must know you are going to have to talk to the manufacturer.

Far as pigment and dye..a dye absorbs into the material and colors it from the inside out. A pigment colors just the outside and is not absorbed by the base material. At least that is what I have always been told is the difference.

I thought dyes were liquid added to the mix while pigments are natural occurring powder type substance??...Lol I dont know. Either way I think it should be OK. If you go to Big Box Stores you will see many bricks and blocks that they sell to be used for raised planters and such

Masons commonly add pigment (different powders as bamboo rabbit says) to mortar to tint it attractively. Maybe a visit to a masonry supply specialty store would enlighten.

But I would think "cheap", rather than "exotic" for these pigments- hard to imagine bulk quantities of cadmium yellow being used, quite easy with iron oxide!