What are lava rocks?

Lava stones are essentially represented by the basalt. Basalt is formed of a mix of tiny crystals (Plagioclase, Pyroxene, Olivine and sometimes Amphibole) that have solidified during the eruption. The melted compound turns little by little into a plastic compound till it has reached a solid consistency. Crystals that solidify at higher temperatures (with a higher content of iron and magnesium) take shape at first place; as a consequence when the rock is completely solid they appear to be larger and defined (fenocrystals). They are easily recognisable to the naked eye. They are often Pyroxenes and Olivine, of red or green colour and bright when they are observed at sun light. The surface blend is also formed of unnumbered tiny crystals (at higher content of silica) that have solidified afterwards at lower temperatures, therefore they have had to adapt to the remaining spaces.   

Consecutively see also some of the following sites of didactic and scientific nature dealing with volcanoes, basalts and lava stones in general:

• http://www.volcanoes.com/
• http://www.geology.sdsu.edu/how_volcanoes_work/Indy.html
• http://geology.com/rocks/basalt.shtml
• http://en.wikipedia.org/wiki/Basalt