There are apparently different answers to this question depending on what you mean.
According to Wikipedia, "Quartz ... is the most abundant mineral in the Earth's continental crust (although feldspar is more common in the world as a whole)."
But Wikipedia also says "On Earth, silicon is the second most abundant element (after oxygen) in the crust, making up 25.7% of the crust by mass."
Possibly also interesting is that the article Earth's most abundant mineral says that "With high-pressure experiments, Knittle and Jeanloz have shown that a mineral called magnesium silicate perovskite makes up most of the lower mantle. And since this region accounts for about two-thirds the bulk of the earth, the researchers believe that magnesium silicate perovskite is the "most abundant building block of the whole planet.'"
Hope you find that helpful...