In which of the following ways does the mineral biotite [BY-uh-tyt] differ from the mineral muscovite [MUHS-kuh-vyt]?

W) Biotite contains silica while muscovite does not

X) Muscovite contains potassium while biotite does not

Y) While both contain aluminum, only biotite contains magnesium

Z) While both contain sodium, only muscovite contains aluminum
Y) WHILE BOTH CONTAIN ALUMINUM, ONLY BIOTITE CONTAINS MAGNESIUM