In geotechnical engineering practice,accurate geological data is essential element for safe and economical design.Since the geology in the Tuen Mun to Tin Shiu Wai Areas is complex,a correct definition of rock classification as well as accurate geological modeling is crucial to support subsequent building and infrastructure developments.The currently adopted rock classification is fundamentally flawed which has created some incorrect rock characterization.According to detailed chemical analyses and accurate field observation data,the need for a correct rock classification for the industry to follow is established in order to advance urban development.