silica: a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechatelierite
oxide: any compound of oxygen with another element or a radical
sundacarpus amara: a large fast-growing monoecious tropical evergreen tree having large glossy lanceolate leaves; of rain forests of Sumatra and Philippines to northern Queensland