Rock formed from the cooling and solidification of molten rock called magma. The acidic nature of this rock type means that areas with underlying igneous rock are particularly susceptible to the effects of acid rain. Igneous rocks that crystallize slowly from magma below the Earth's surface have large crystals. Examples include dolerite and granite.
Red stands for hardiness and valour. White signifies purity and innocence. Blue represents vigilance, perseverance, and justice. The latest star, representing Hawaii, was added in 1960. Effective date: 4 July 1960.