Looks like this small rock was broken at a mineral filled fracture. Previous fracture fills is Gale crater have identified as forms of calcium sulfate. We’ll have to wait for any released analysis to see what the science team make of these rocks and their mineral filled fractures.

This raw image is a focus stacked MAHLI image from sol 4711. The focus stacked images are assembled on the rover and returned to Earth, this saves the number of images that require sending as bandwidth are limited

Credits: NASA/JPL-Caltech/MSSS