I have this around my yard between larger concrete stepping stones and in more open locations. It is a rough rock with hints of different colors. My guess is some sort of gravel - I'm hoping for something more specific to purchase more.
White color makes it very likely to be mostly lime stone. The size looks like limestone "screenings" . When limestone is crushed certain size ranges are used for concrete ; so sizes are separated by screens . The angular shape also indicates a crushed material. This is size is too small for concrete and is essentially a by-product. Smaller "dust" size particles have been washed away. If you only want a few pounds , you can get a similar ( but expensive) product at pet shops as "crushed coral" or aragonite . Aragonite is one of the crystal forms of calcium carbonate.