This industry comprises establishments primarily engaged in the merchant wholesale distribution of coal, coke, metal ores, and/or nonmetallic minerals (except precious and semiprecious stones and minerals used in construction, such as sand and gravel). Cross-References. Establishments primarily engaged in-- ? Merchant wholesale distribution of nonmetallic minerals used in construction, such as sand and gravel--are classified in Industry 423320, Brick, Stone, and Related Construction Material Merchant Wholesalers; ? Merchant wholesale distribution of crude petroleum--are classified in Industry Group 4247, Petroleum and Petroleum Products Merchant Wholesalers; and ? Merchant wholesale distribution of precious and semiprecious stones and metals--are classified in Industry 423940, Jewelry, Watch, Precious Stone, and Precious Metal Merchant Wholesalers.