“A cave entrance?” you ask. It might seem ordinary but even this simple cave entrance, the entrance to \u7926\u6d1e, speaks volumes about Hong Kong’s surprising geological history.
Hong Kong. It may be small but it possesses a wealth of mineral deposits. Mesozoic igneous activity played a huge role. Hydrothermal activity enhanced mineral concentrations. Faulting also helped in the formation of the \u7926\u6d1e.
For centuries locals have used clay for pottery. Archaeological discoveries suggest iron smelting happened during the Tang dynasty around 900 years ago. Organized mining began in the late 19th century. Initially miners focused on two lead deposits. Silver and alluvial tin deposits were also reported. An iron mine opened at Ma On Shan in 1906. Many small surface workings show there was prospecting activity. Uncontrolled mining operations likely occurred before regulations.
Hong Kong’s natural resources include metalliferous veins. Non-metalliferous industrial minerals exist onshore. There are also quarried rock and building stone. Offshore sand deposits are also present.
Sporadic Sn–W–Mo mineralization can be found in Hong Kong. It mainly occurs in pegmatites veins and greisen in granite contact zones. It can also be found along northwest-trending faults. Fine-grained granites often host Sn–W–Mo mineralization. The Needle Hill Granite and the Chek Lap Kok Granite hold the richest deposits.
Quartz veins at the Needle Hill mine were worked for wolframite. The mine produced 1000 tonnes of wolframite concentrate from 1938 to 1967.
Cassiterite has been found in several areas. These areas are Sheung Tong Needle Hill and Devil’s Peak. It has never been commercially exploited. Wolframite was mined at Needle Hill Lin Fa Shan and Sha Lo Wan. Minor workings occurred at Castle Peak and Devil’s Peak. Molybdenite often accompanies wolframite but hasn’t been commercially exploited.
Pb–Zn–Cu mineralization is mainly associated with epithermal veins. These veins are located in coarse ash crystal tuff in the New Territories and on Lantau Island. The richest deposits are near major northeast-trending shear zones. Pb–Zn ore was mined at Lin Ma Hang. Small-scale mining occurred at Tai Mo Shan Silver Mine Bay and southeast Lantau Island.
Quartz veins at the Lin Ma Hang mine contain galena pyrite sphalerite and chalcopyrite. The veins intrude the Tai Mo Shan Formation. The mine operated intermittently from 1915 to 1958. It produced 16000 tonnes of lead metal and 360000 ounces of silver.
Silver is also found within galena at Silver Mine Bay on Lantau Island. Chalcopyrite is present in small quantities. Sphalerite and galena have been reported in wolframite-bearing quartz veins. These veins are located at Needle Hill Lin Fa Shan and Devil’s Peak.
Fe mineralization exists in many areas. The largest deposit is at Ma On Shan. Magnetite was mined from a granite-related calc-silicate skarn deposit. The mine produced over 3 million tons of processed ore. Remaining ore reserves are estimated at 4 million tons.
High-quality feldspar used to be mined at Tung Lo Wan Sha Tin. The mine was abandoned in 1984. Feldspar was also mined at Cha Kwo Ling.
Quartz was mined from residual granitic soils and thick quartz veins. Smaller operations working quartz veins existed at various locations.
Beryl has been reported in wolframite-bearing quartz veins. These veins are located within hydrothermally altered fine-grained granite in the Devil’s Peak area. The deposit has not been commercially exploited.
Graphite interbedded with other rocks was once mined on West Brother island. The mine operated from 1952 to 1971.
Granite was used for dressed stone. It is no longer used for that purpose. Local volcanic rocks are more resistant to weathering. Granite and volcanic rocks have been quarried for road base metal and concrete aggregate. Two quarries are currently operating in Hong Kong.
So next time you see a cave entrance like this remember the hidden story of Hong Kong’s dynamic geological past.