Schwenzer suggested the smooth shapes "could be due to diagenesis or more generally water-rock interaction." Diagenesis refers to the alteration processes that occur after sediment is deposited. Curiosity has been investigating a clay-rich area of Mars. Data gathered there is helping scientists delve into the history of water on Mars.
If you're trying to figure out the scale here, think tiny. The ChemCam Remote Micro-Imager is capable of taking super-close-up images. The ChemCam team analyzes soil and rock composition and investigates weathering processes.
Curiosity has been gifting researchers with a diverse array of rocks lately. "The rich workspace included bedrock, pebbly areas and a brighter float rock of a kind which has been observed frequently in the vicinity," Schwenzer wrote.