Related Clues:

• Tram car fillers
• Graded materials
• Rich rocks
• Refinery needs
• Mined rocks
• Metal containers?
• Gold and silver, e.g.
• Gold or silver sources
• Bauxite et al.
• Miner's discoveries
• Metal-in-the-rough
• Lode stones
• Bauxite and borax
• Metallurgist's materials
• Sources of silver