Talc, the softest known mineral, is sectile — you can cut it with a knife. Gold is another sectile mineral that is relatively easy to cut. Modeling clay is sectile, too. So is fudge, but that's too obvious for people to mention!
Sectile comes from the Latin root secare, meaning "cut." And speaking of Latin, you may also read about opus sectile, a style of ancient Roman mosaic art for floors and walls. Instead of using an immense number of tiny pieces of all the same shape, opus sectile involved cutting pieces of stone, shell, or mother-of-pearl into different shapes to form a design. Opus sectile mosaics can still be found in some European churches built during the Renaissance. Opus means "work."