Which of the following pairs of minerals is NOT part of the same nonsilicate mineral group?

A) calcite and dolomite
B) hematite and magnetite
C) pyrite and galena
D) plagioclase feldspar and potassium feldspar

Plagioclase feldspar and potassium feldspar are both silicate minerals, belonging to the feldspar group, which is the most abundant group of minerals in the Earth's crust. The other pairs listed are nonsilicates and belong to different mineral groups: calcite and dolomite are carbonates, hematite and magnetite are oxides, and pyrite and galena are sulfides.