Chalk produce, and thus widely used in the developing world, calcium-based chalk can be made where the crumbling particles are larger and thus produce less dust, and is marketed as "dustless chalk". Colored chalks, pastel chalks, and sidewalk chalk (shaped into larger sticks and often colored), used to draw on sidewalks, streets, and driveways, are primarily made of gypsum. Chalk is a source of quicklime by thermal decomposition, or slaked lime following quenching of quicklime with water. In southeast England, deneholes are a notable example of ancient chalk pits. Such bell pits may also mark the sites of ancient flint mines,
Blackboard Inc. and notifications, academic or instructor notifications, or by school districts and communities to share time-sensitive information, such as in the case of natural disasters and campus emergencies. Blackboard Transact, formerly Blackboard Commerce Suite, is transaction processing system tied to university ID cards, which can be used for meal plans, vending machines and laundry services, and an e-commerce front end for the transaction system. The Transact system is NFC-compatible and its ID cards use contactless technology. Blackboard Transact also includes a program for off-campus vendors that allow students to pay for goods using their college's campus card. Blackboard Analytics was developed