On the marine erosion platform about 1 km southeast of Chiyu, there is a series of rock dikes extending to the north. These dikes are alkaline basalt, densedark in lithologyrich in olivinepyroxene agglomerates, which were captured when the lava flow erupted. It is the best place to know olivinepyroxene in the Penghu area. As its appearance is completely different from the general basalt, the local residents think it is something from abroadthe word "fan (foreign)" is crowned. So, it is called "fanzi stone". The olivine mass basalt is caused by the eruption of alkaline basalt lava. During the ascent of lava, the olivine around the lava chamberslava eruption channels is captured. Among these captured rock blocks, the color of olivine is generally yellow-green,pyroxene minerals are dark green. Sometimes, larger olivine crystals may be seen as well. There are moreless olivines in the alkaline basalt of Penghu, with “fanzi stone”Chabo Islet being much more enriched with many olivine agglomerates. The specimens collected by this center are from Chiyu, Huxi Township.