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Photographs are of limited utility for rock and/or mineral identification. It is near impossible to correctly observe a mineral's luster (which is often diagnostic) from a static photo.
That said, the overlying "white" you speak of is mostly likely quartz of a different genesis than the underlying quartz (simply because SiO2 is the most common mineral). Alternatively, and near equaly likely, the "white" is plagioclase or calcite. Impossible to tell without having the sample in front of me; however, exceedingly easy to tell with 100% confidence if the sample was in front of me (or any other geologist or mineralogist).
Best... L.G.