(1/47)  A typical anorthosite looks less exciting. The only striking thing is that the rock consists of only one mineral. If you move the sample, it glitters everywhere. This means that the mineral has cleavability, i.e. it will probably be feldspar. (Because it is quite obviously not a dark mineral and also not a mica - the other candidates for minerals with cleavability). So the next question is: which feldspar?

(Calcite would also be possible, which would make the rock a marble. Calcite, however, is rather brightly coloured and can easily be recognized by it's low hardness and the violent reaction with hydrochloric acid.)