Lava Chemistry and minerals
Lavas are the eruptive equivalent of intrusive igneous rocks. Chemical and mineral contents are the same and it is texture and crystal formation which makes them appear different. Igneous rocks cool slowly within a magma chamber and crystals are able to grow . Lavas cool quickly and crystals do not have time to grow large giving a finer texture. Larger crystals from the magma chamber are erupted with the lava and are are called phenocrysts.
The table below gives examples such as Rhyolite is the eruptive form of granite. The word sin pink are the names of the minerals. Quartz is Si O2 (silica oxide) silica plays a major role in the colour,density and viscosity of igneous and volcanic rocks. More silia lighter,less dense and viscous less silica and maore Iron darkcolour,high density aand low viscosity.