As an intrusive rock, the elements are absorbed into granite's surface pattern.
Granite is an igneous rock, which means that it's related to volcanic elements just under the earth's crust. It's formed by the cooling and solidifying of magma, collecting other minerals to produce the grainy pattern that distinguishes it from other rocks. Granite colors are unique and traceable to its origin location by the mineral content. Differences between older and younger granite are a result of environment conditions that occur over time as granite slowly erodes.
Weathering
Physical weathering is a natural occurrence with seasonal weather conditions; winter frost can wedge between layers of rock and expand when it freezes, changing the rock's shape and size. In some cases, environmental conditions, like rain, can cause chemical reactions that are acidic, altering the mineral content and disintegrating the granite. Overtime obvious changes in composition between older and younger granite becomes visible.
Erosion
Granite contains a percentage of quartz and feldspar and is susceptible to the environment. When feldspar comes into contact with acid and water, it will convert to clay and quartz and will become eroded down to a fine sand. Nature's elements of wind and rain affect the surface of granite, especially with higher levels of exposure. The hardness of granite makes erosion a slow and tedious process for older and younger granite.
Thermal Expansion
Temperature changes that occur repeatedly from hot to cold cause the rock to expand and contract, changing the rock's structure. Radiant heat or natural fires cause the minerals to breakdown, changing the inner layer appearance and mineral forms. Sectional cuts in older granite appear more weathered, with breaks or veins running through the rock. Younger granite retains an inner layer of coarse crystals.
Oxidation
Red coloring in granite comes from a presence of iron, which gives it a reddish-brown color. Environmental water that seeps into the rock's core with exposure to oxygen causes oxidation, or rusting. Outer surfaces are broken down, covering the rock's surface with layers of red, yellow or brown-colored substances, making no distinction between older or younger granite.
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