The mineral most frequently found in both granitic continental crust and basaltic oceanic crust is feldspar.

Here's why:

* Feldspar is a group of rock-forming minerals that are extremely common. They are a major constituent of both igneous and metamorphic rocks.

* Granitic continental crust is typically rich in quartz and feldspars (both potassium and sodium feldspars).

* Basaltic oceanic crust also contains significant amounts of plagioclase feldspar (a type of calcium-rich feldspar).

While other minerals like quartz and pyroxene are also present in both types of crust, feldspar is the most abundant and widespread.