||The geology of the Samdeok Mo deposit consists of Paleozoic Hwajeonri formation, Kowoonri formation, Suchangri formation, Iwonri formation, Hwanggangri formation, leucocratic porphyritic granite and granitic porphyry. This deposit consists of 3 quartz veins that filled NS oriented fractured zones in Suchangri formation. Quartz veins vary from 0.05 m to 0.3 m in thickness and extend to about 400 m in strike length. Quartz veins occur as massive, breccia, and cavity textures. Wallrock alteration has silicification, sericitization, argillitization and chloritization. The mineralogy of the quartz veins consists of quartz, fluorite, white mica, biotite, apatite, monazite, rutile, ilmenite, molybdenite, chalcopyrite, Fe-Mg-Mn oxide and Fe oxide. White mica from Samdeok Mo deposit occurs as fine or coarse grains in quartz vein and hostrock and has 4 mineral assemblages (1. quartz, molybdenite, Fe oxide and Fe-Mg-Mn oxide, 2. quartz, Fe oxide and Fe-Mg-Mn oxide, 3. quartz and biotite, and 4. quartz). The structural formular of white mica from quartz vein is (K0.89-0.60Na0.05-0.00 Ca0.01-0.00Sr0.02-0.00)0.94-0.62(Al1.54-1.12Mg0.36-0.18Fe0.26-0.09Mn0.04-0.00Ti0.02-0.00Cr0.02-0.00Zn0.01-0.00)1.91-1.72(Si3.40-3.11Al0.92-0.60)4.00(OH1.68-1.42F0.58-0.32)2.00, but white mica coexisting with quartz, molybdenite, Fe oxide and Fe-Mg-Mn oxide has higher FeO content, and lower SiO2 and MgO contents than white micas with other mineral assemblages. Also, compositional variations in white mica from the Samdeok Mo deposit are caused by phengitic or Tschermark substitution ((Al3+)vi+(Al3+)iv <-> (Fe2+ or Mg2+)vi+(Si4+)iv) and direct (Fe3+)vi <-> (Al3+)vi substitution.