Silicic is an adjective to describe magma or igneous rock rich in silica.
The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent.
These are just part of all the other silicate minerals that make up 90% of the earth's crust.
This broad classification is refined in practice based on more detained compositional studies where ever possible in the science of mineralology.
The "Shammar group" is a silicic and volcaniclastic sequence in northwestern Saudi Arabia.