buhrstone, also burrstone /bûrˈstōn/

1. A variety of quartz, containing many small empty cells, which give it a roughness of surface particularly adapted for millstones
2. A millstone made of this

• thralling
• thralls
• thrang
• thrapple
• thrappled
• thrapples
• thrappling
• thrash
• thrashed
• thrasher
• thrashers
• thrashes
• thrashing
• thrashing-floor
• thrashing-machine
• thrashing-mill
• thrashings
• thrash metal
• thrasonic
• thrasonical
• thrasonically
• thrave
• thraves
• thraw
• thraward