chert

"Brush your teeth."

"The arrowhead was chipped, making the arrow unsafe to use. "

"Except for one or two days a year, he usually walks to work."

"The artisan carefully polished the piece of chalcedony until its milky translucence caught the light beautifully. "

"He listened carefully to his mother's concerns, feeling sorrowful about her disappointment. "

"The archaeologist carefully brushed dirt away from the ancient pottery. "

"We could color the walls red."

"I recognised his face immediately."

"karst massives in western Georgia"

"The forest canopy created an opaque that blocked out the sun. "

"The geologist found a beautiful mineral specimen in the rock collection. "

"The hiking trail was made of crushed quartzite, which sparkled in the sunlight. "