Possible Clues:

• Opaque vase material
• Vase material named for its white color
• Vase material
• Whitish vase material
• Porcelain-like material used in vases
• Opaque drinking vessel
• Porcelainlike material used in vases
• Gallons pinched by dairymaid? It's not entirely clear
• Opaque material used in vases, e.g.