Under most weathering conditions, which mineral component of granites and rhyolites would be most resistant to decomposition?

Granite would be more resistant to decomposition as compared to rhyolite because rhyolite is a fine-grained rock and Granite is a coarse-grained rock. 

Granite tends to be more stable to weathering conditions. The major component of quartz, orthoclase, muscovite and biotite are the in order of resistant to decomposition.