A meteorite can be composed of different materials and so can vesicular basalt, but because of the presence of pores in vesicular basalt a meteorite would likely be heavier, assuming that they have the same volume.
On the Moh's hardness scale, basalt has a hardness of 8. Anything between 5-10 is considered hard. Materials on the scale between 1-3 are considered soft, and anything rated from 3.5 to 5 is considered medium-hard.
Yes. Basalt occurs only in the crust; the oceanic crust is primarily basalt. Actually the mantle contains far more basalt than is in the entire crust. the oceanic crust is mostly basalt the continental crust is mostly granite
I am not sure what you mean by "smaller" BUT - Most piles of basalt on the planet (eg hawaii) are in water - Indeed the whole oceanic seafloor is basalt, so there is more basalt in water than ALL the basalt to be found on land.