There isn't a single "main mineral" of land. The Earth's crust is incredibly diverse and made up of a wide variety of minerals.

However, if we're talking about the most abundant minerals in the Earth's crust, the top contenders would be:

* Feldspar: It's the most common mineral, making up around 60% of the Earth's crust. It's found in many types of rocks, including granite and basalt.

* Quartz: This is the second most abundant mineral, making up about 12% of the Earth's crust. It's found in many types of rocks, including sandstone and granite.

So, while there's no single "main mineral," feldspar and quartz are the most abundant minerals found in the Earth's crust.