When the vesicular basalt is immersed in seawatergroundwater, various carbonate minerals will enter the poresfissures of the rock formationthen begin to precipitatefill the pores. Some calcium carbonate minerals are mainly aragonitecalcite, in addition to magnesium, iron, manganeseother carbonates, as well as limonite, siderite, magnesite, opal, quartzso on. Aragonite is mainly composed of these materials. Although aragonite has low hardnesspoor acidalkali resistance, it is quite rarehas beautiful patterns. After being groundpolished, it shows concentricirregular lines, bright colors,unique patternscan be processed into various ornaments, which look so elegant that people will definitely like them. The reason why aragonite forms is that the colloidal substance of aragonite is precipitated at low temperatureis a kind of regenerated filling mineral. In other words, the basalt lava solidifies first,then aragonite is gradually deposited into the porescracks. In particular, basalt with more ironmagnesium minerals contains aragonite in its geodes. Penghu’s aragonite is mainly formed in Fenggui, Shili, Houliao, Tongliang, Hejie, Chixi, Waian, Wangan Islet, JiangjiyuenyuDongjiyu. Among them, the aragonite formed in Wangan IsletJiangjiyuenyu is of the best quality, with groups of concentric circles, which are called “aragonite eyes”. This aragonite-bearing basalt specimen was collected from Tongliang of Paisha Township.