Alkaline basalt is a common rock in Penghu, mostly dark black in color, sometimes browndark red when oxidized. Its most common composition granularity is densefine crystalline. Its main constituent minerals are plagioclase, olivine, titanitegranular magnetite. Its silicon dioxide content is low, mostly less than 49. The magma is produced by the partial melting of the upper mantle material, at a depth of about 80 kilometersat an average temperature of about 1250℃, so the magma comes from the deeper mantle. Due to the relationship between the magma compositionrapid cooling, the ejected magma forms a columnar volume that is relatively small, generally about 50 cm in diameter. Alkaline basalts are widely distributed,those at JishanyuDinggouyu are the most beautiful. The alkaline basalt specimens in this center were collected from Cingluo Village, Huxi Township.