A small piece of sample collected from a contact calcium-skarn aureole in San Shek Wan of Lantau Island surprisingly shows abundance of Thorium (Th) and Rare Earth Elements (REEs). Concentration of these trace elements in skarn is of special interest for its impact to human health and its economic values. Concentration of these elements in skarn is closely related to the tectonic setting, the initial magma chemistry and the depth of magma intrusion where the skarn is being formed. These variables in skarn formation process can be analyzed by studying the geology of the area, accompanied by analyzing mineralogy of the skarn. Mineral zoning of garnet-pyroxene prograde skarn and chemical zoning within garnet crystal also provide clues to the pressure-temperature condition when the skarn aureole was formed. Impact of these elements to human health is evaluated by abundance of these elements exposed and assessed through various means – radiation, inhalation and ingestion. / published_or_final_version / Applied Geosciences / Master / Master of Science