corundum

"The jewelry box was filled with colorful gemstones like rubies, emeralds, and sapphires. "

"The liftoff will occur in exactly twelve seconds."

"I went to the park because the weather was nice. "

"The weather was extremely hot today; we stayed inside all afternoon. "

"The mechanic used an abrasive to smooth the rough edges of the metal pipe. "

"My bicycle's frame is made of aluminum. "

"The formula for calculating the area of a rectangle is length times width. "

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

"The hardness of the diamond makes it ideal for cutting glass. "

"Before painting the walls, she used sandpaper to smooth out the rough spots. "

"The scientist studied the chemical composition of the soil sample. "

"My grandmother's necklace featured a beautiful sapphire, reflecting the light beautifully. "