A gravel factory where you can crush your stones into crushed stone (mixed gravel). The crushed stone/mixed gravel can then be sorted into gravel (coarse), fine gravel and sand. Further processing of coarse gravel gives fine gravel, and fine gravel can be ground into sand.

Gravel Factory
Input: Stone
Output: Crushed Stone, Gravel, Fine Gravel and Sand
Price: $25000

Gravel and Sand Sellpoint
Input: Crushed Stone, Gravel, Fine Gravel and Sand
Price: $100