
Basalt has the feature that pillar-shaped joint is hereby shown. It is lined up in order and form a magnificent view. In addition, during the formation, basalt can take a fine-dense form or a porous form. The porous form is made by the stomas left by magma crystal after its evaporate gas is eased. These stomas are filled by the mineral sediment of polychrome carbonic acid anion. Most of them are Graupel stones, and they are unique precious stones of penghu, also known as stones with pleasing streaks or mottles. The similar stones can only be seen in Italy.