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200 m to the south, there is a irregularly-shaped xenolith of porphyritic medium-grained granite, with feldsparcrystals up to 50 mm long. The granite is cut by thin basalt dykes and by feldsparphyric rhyolite.Discovery Bay. Megacrystic fine-grained granite is exposed in cut slopes (1930 1740) west of the ferry pier atDiscovery Bay. The granite is pinkish-white, with alkali feldspar megacrysts up to 40 mm long, and single biotitecrystals 1 to 2 mm long. The fine-grained granite is intruded by feldsparphyric rhyolite dykes.Man Kok - Trappist Monastery Kaido Pier. The country rock around Man Kok is dominantly fine-grainedgranite and variably megacrystic. The granite is greyish white with pink feldspar megacrysts up to 30 mm. Biotiteoccurs as single flakes or clusters of crystals up to 3 mm and the groundmass is dominantly 2 to 4 mm. The granitebecomes pegmatitic in parts, and commonly contains dykes of aplite. Patches of fine-grained granite occur close tothe contact with fine-grained granite near the monastery jetty.Silver Mine Bay. Between Silver Mine Bay and Chi Ma Wan, there are easterly-trending bands (up to 200 mwide) of altered granite and rhyolite dykes, separated by zones of relatively fresh rock. The altered granite iscommonly megacrystic and fine-grained, and is cut by quartz veins along the main ridge of hills (1838 1292).South of the South Lantau Road there are exposures of equigranular to sparsely megacrystic, fine-grained granite.The rock is typically slightly greenish-white, and weathers to a pale brown. Quartz megacrysts up to 4 mm areprominent on weathered surfaces, and pink feldspar up to 10 mm are also present.At the east end of Pui O Wan beach, a valley marks a change from equigranular fine- to medium-grained granite inthe south, to fine-grained granite in the north. Contact relationships are not exposed. The fine-grained granite atthis locality is megacrystic and is cut by feldsparphyric rhyolite dykes.Hei Ling Chau. The granite on Hei Ling Chau is dominantly equigranular and fine-grained although it may containpatches of medium-grained granite and pegmatite. Although not usually megacrystic, some parts contain prominentquartz and feldspar megacrysts; the feldspar can be up to 30 mm.Cheung Chau On the northwest coast (2072 0908), there is a small patch of fine-grained granite and pegmatiteless than 1m by 3m. The fine-grained granite grades into the adjacent medium-grained granite. Pegmatite veins inthe medium-grained granite are exposed out about 120 m to the south, as are thin veins of finer granite andpegmatite in a cut slope (2072 0859) south of Tai Kwai Wan.Shek Kwu Chau Exposures of megacrystic fine-grained granite are present in the southeast of the island, adjacentto outcrops of medium-grained granite, although the contact between the two is not exposed, Feldspar megacrystsin the fine-grained granite are up to 25 mm long, whereas quartz megacrysts are up to 6 mm across. The megacrystsare set in an equigranular groundmass. Aplite and pegmatite veins cut the granite, and there arc localized biotiteconcentrations. Exposures on the coast, about 120 m east of the jetty (1743 0627), comprise pinkish-grey,megacrystic, fine-grained granite which are cut by aplite dykes up to 0.3 m across. Both the apiite and the graniteare cut by a 1 m-wide feldsparphyric rhyolite dyke.Chek Lap Kok (prior to development). Inequigranular, non-megacrystic to sparsely megacrystic, fine-grainedgranite crops out west of a line from Sham Wan to Fu Tei Wan. The granite is light pinkish-grey in coastalexposures, and grey when fresh. Quartz megacrysts, up to 5 mm, are only rarely seen. Single flakes of biotite,mostly from 1 to 3 mm, are a prominent feature of the rock. The grains of the groundmass are between 0,2 and 2mm, but are mostly around 1 mm.Sample HK8362 (1101 1976) from Cheung Sha Lan is typical, displaying single biotite flakes up to 2 mm. Therock exposures at this locality are relatively free of joints and appear to have been extracted for building stone.Sample HK8363 (1069 1905) from the borrow area for the test embankment is a liner-grained variety of granite(microgranite), and this lithology dominates the borrow. Much of the construction material for the test embankmentis fine-grained granite, but blocks of fine- to medium-grained granite, and rarely medium-grained granite, are alsopresent.San Shek Wan - Sha Lo Wan. At the northern end of the beacon at San Shek Wan (0714 1612), approximately100 m north of the jetty, there is an exposed contact between granite and metasedimentary rocks. The granite is amegacrystic, fine-grained variety, and the contact with Carboniferous strata to the south strikes eastnortheast anddips 74 south. The contact is marked by a 5 m-wide zone of skarn containing garnet, vcsuvianitc, diopside andepidote (Peng, 1978). The contact zone also includes quartz syenite and lamprophyre (vogesite) dykes,Tin Sam. Pinkish-grey, megacrystic fine-grained granite is exposed on the coast west of Hau Hok Wan, Biotiteoccurs as individual crystals between 1 and 2 mm across, and the rock is cut by thin aplite dykes, numerous thinquartz veins, and occasionally pegmatitic patches, *72