Chalk /ˈtʃɔːk/ is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores.
This briefing presents the first graphic we’re aware of that aggregates the disparate systems of confinement in this country, which hold more than 2.4 million people in 1,719 state prisons, 102 federal prisons, 2,259 juvenile correctional facilities, 3,283 local jails, and 79 Indian Country jails as well as in military prisons, immigration detention facilities, civil commitment centers, and prisons in the U.S. territories.
A “normal” incandescent bulb costs about 0.75cents per hour, and LEDs or CFLs cost only one-sixth of that – so leaving the lights on (either overnight or while you’re at work for the day, say both are about 8 hours) costs you roughly 6 cents for a normal light and a bit over 1 cent for modern bulbs.