What is the classification of a congretion rock?

Question

best answer will be choosen if u can tell mii the structure density and weight

Answer 1

There is no such hting as a "congretion" rock.

Answer 2

I think you mean 'concretion'.  In which case, there is a pretty good article on Wiki that discusses the topic.

http://en.wikipedia.org/wiki/Concretion#...

Concretions are merely minerals that have precipitated in sedimentary rock (possibly in void spaces) and are generally ovoid in shape.  They're pretty common in fine-grained clastic or carbonate rocks, I've found lots of them.

As far as density goes, it depends on the mineral that has been precipitated.  Common minerals are silica, calcite, goetite, and hematite.  You can find their densities easily on the net.  Weight would depend on the size (or volume) of the concretion.