Looking like a vase, Pinnacle is a 0.0308-square-kilometer islet with a sharp tip. Formed by a small islet and many coral reefs, the islet, which is about 180m long and 80m wide and with an elevation of 51km, is 31.7216km away from Bitou Cape. Local fishermen call it the Kangjiao Yu (sedan islet), as it looks like a sedan from the northeast.

　　Pyroxene and andesite are the major rock types of the zigzag vase islet. The entire islet is coved with metallic volcanic debris which has turned purplish red (bordeaux), purple, green, brass (yellowish) and iron grey after oxidation. When sunlight sheds on, the reflection on the sea glitters like a kaleidoscope and corresponds to the Mianhua Islet (Crag)and Pengjia Islet (Agincourt). The abrasion cave on the fault in the southeast is the best evidence of the lifted abrasion platform.