Explanation: In igneous and metamorphic rocks minerals may occur in the cracks, crevices, faults or joints.

• The smaller occurrences are called veins and the larger are called lodes. In most cases, they are formed when minerals in liquid/ molten and gaseous forms are forced upward through cavities towards the earth’s surface.
• They cool and solidify as they rise. Major metallic minerals like tin, copper, zinc and lead etc. are obtained from veins and lodes.

Source: NCERT