GeologyRocks

Interesting.  It would help to know what the other rocks in the vicinty look like but at first sight I would say it's flint as there is evidence of conchoidal fracturing on some broken surfaces.  The orange stuff could be holes in the flint infilled with iron minerals for example.

It is a little hard to tell. What is the scale (put a ruler against it before photographing)?

It looks like either a piece of flint, but since flint tends to develop a white coating, a better possibility is a piece of obsidian, that is volcanic glass. But if you can say where it is from, with some detail, then it may be possible to say more. I guess you have got it either from a beach or a river deposit, because the rock is well-rounded. 

Is it a volcanic area?  I'm not familiar with the geology there. but it looks like basalt (again???).  Is it heavier than you would expect?  In your mind compare it to the same volume of water.  How much heavier is this rock?

John

“Civilisation exists by geological consent, subject to change without notice.” -  Will Durant