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. distance learning and for conferencing. The company launched Blackboard Mobile in 2009 after having acquired TerriblyClever. The platform provides students with access to teaching and learning content and campus information through mobile applications for iOS, Android, BlackBerry and WebOS devices. Blackboard Mobile allows students to both access course materials, check grades, and participate in discussions, and to access information about campus life and services. The company began providing its Blackboard Connect service in 2008, for use by school districts and higher education institutions to send out mass phone, text and e-mail notifications. The service can be used for routine alerts