Sandstone is a kind of sedimentary rock, mainly composed of sand particles, of which more than 50 are sand grains. Of the same color as sand, sandstone can have any colors, of which the most common is brown, yellow, red, graywhite. Besides basalt, thick-bedded sedimentary rock is another major rock that constitutes the Penghu Islands. The interbedded outcrops of sedimentary rockbasalt are most commonly seen in Siyu, especially in the areas of WaianNaian. These loose sandstonesmudstones were deposited along the seaside about 10 million years ago. In addition, judging from the sedimentary structurelithology, the depositional environment of these rock formations should be shallow seas, tidal flatsswamps, indicating that the basalt lava flowed to the shallow sea area at that timewas then covered by the sediments brought by the seawater. The specimens collected by this center are from Dongyuping of Wang-an Township.