Complex sentence: Dvaraka silas are coral with chakra (wheel) markings and the chakra-mark is the most distinguishing feature of these stones, and hence they are called "chakrankita-sila".
Split into simpler sentences: Dvaraka silas are coral with chakra (wheel) markings. The chakra-mark is the most distinguishing feature of the Dvaravati stones, and hence they are called "chakrankita-sila".