Does it ever just blow your mind that lava is runny rock?
1969-1974 Mauna Ulu Eruption, Kīlauea Source: USGS volcanoes.usgs.gov/volcanoes/kila
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I've always wondered ... what kind of rock is lava? Like what kind of mineral is it?
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Lavas contain a bunch of different minerals and the rock types are different :) Any good volcano answer: it depends and it's complicated.
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So some lava can have a higher melting temperature than other lava based on the composition of the rock?
Yes! Generalization: iron rich lava has a lower melting point than silicon rich lava, and is runnier, less likely to cause a volcano to explode, and builds volcanoes that aren't as steep. Mt St Helens: more silicon. Hawaii: more iron. (I'm an enthusiast, not an expert.)
Yes! Lavas with higher silica (like dacites and rhyolites) melt at lower temperatures than lavas with more magnesium and iron (such as basalts). Volatile content (CO2, fluorine, water, etc.) can also affect the melting point of a lava.
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