The term "granite" comes from the Latin word "granum" - a grain, because granite is made of lots of smaller bits of quartz, mica and feldspar stuck together. Granite is an igneous rock, formed from hot, molten magma. The magma is forced between other layers of rock by high pressure beneath the Earth's surface. The magma cools and turns slowly into solid rock. Granite has many different types of minerals in it and as the magma cools these minerals form crystals.
When you look closely to a piece of this Phia Oac granite, you will see white and often translucent grains which is quartz, a mineral composed of silicon and oxygen. Also you will observe black shiny grains of mica, a minerals that crystallizes into flat sheets. The other important component of granite is feldspar which can be reddish or pale pink.
When molecules of aluminum, silica and oxygen combine with potassium, they create feldspar. It's a very common mineral: over half of the earth's crust is made up of feldspar!
Approximately 100 million years ago hot magma was present beneath the earth in the Phia Oac area as well as in larger part of Southeast China. This is the origin of the granite. Many minearals, some of them precious and rare, can be found in the granite, for example gold, tin and tungsten. It is this concentration in minerals that explains the many mines that you find on the Phia Oac experience route.