can anyone tell me what the difference between mars black and lamp black oil paint is?

The difference between all of the different "same" colors depends upon the pigment used to get the color. Lamp black uses a burned petroleum residue (I think) to get that particular black. I don't know what Mars Black is pigmented with. There is usually a difference in how well the paint covers between the different pigments, some being more opaque than others.
Hope that helps.--

The black I have has burned animal bones as the pigment. I don't use it because of that reason, wish I had read the ingredients before I bought it. I always say read the instructions first then go to work. I didn't this time and am sorry about it.

Mix it with a bit of white to see the difference in shade and opacity,

Keith

Thanks all for the responses.

And like a lot of similar things on About.com, this isn't reliable ><

Barry, Mars Black is made from an iron pigment and should be the leanest black. It'll tend to dry matt most easily of all the common blacks (both because of the low oil content as well as the shape of the pigment particles).

Lamp Black is nearly pure carbon (literally used to be made from lamp soot). It's probably going to be the blackest of all blacks in practice, but there isn't a huge difference from one black to the next and once you have a matt finish the difference is less noticeable still. In common with all the carbon-based blacks it is high in oil so it's a good natural glazing colour and for where you want a glossier finish.

Mars Black is the most opaque black, but Lamp Black also covers well because it's very strong. Either one should be high or very high in tinting strength; both produce blueish tints, Lamp Black's in particular can be noticeably more blue.

Einion

Thanks Einion, that answers my question spot on.

I've tried both and am happier with the mars black. As Einion said it's got a higher oil content, so it tends to dry with a slight sheen, unless you soak it on a note card for a extended period of time. You will still need to to soak the oil out of the mars black, but, not as long and usually a more reliable flatter finish.Chris

Mike, me thinks it's Ivory Black. Used by the old masters. Not I though.
Chris

Welcome Barry.

I actually said the opposite Chris.

Einion

OOPS! It was suppose to read" As Einion said the lamp black has a higher oil content."
Chris