2 places with osteoprogenitor cells are periosteum and endosteum. Stem cells from periosteum are involved in fracture healing, whereas those in the endosteum are involved in bone remodeling. Source: https://www.kenhub.com/en/library/anatomy/histology-of-bone

Osteoblast: Builds bone by secreting collagen and catalyzing mineralization in alkaline environment via Alkaline phosphatase (ALP). Differentiates from mesenchymal stem cells in periosteum. Osteoblastic activity measured by bone ALP, osteocalcin, propeptides of type I procollagen. (FA)