FTR is a British rapid-transit bus system, currently in operation in Leeds, Luton and Swansea.irst Group has introduced the system, using Wright StreetCar articulated buses in conjunction with infrastructure upgrades by local authorities. The vehicles have been branded as the future of travel, the operators claiming that ftr is textspeak for the word future.
Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3).
Jupiterimages/Photos.com/Getty Images. Limestones are a class of sedimentary rocks composed of the same mineral, calcite, which is made from calcium carbonate, or CaCO3. Despite this similarity in composition, however, not all limestone rocks are the same. Chalk is actually a special form of limestone that exhibits some differences from other rocks in the same class.