Global mining group Rio Tinto has apologized after one of its contractors lost a tiny capsule containing a radioactive substance somewhere along a 1,400-kilometre stretch of road in Western Australia. The capsule, which contains a small quantity of radioactive Caesium-137, is about 6 millimetres in diameter and 8 millimetres tall, Western Australia Health said. It is believed the capsule, last seen on January 12 according to a new statement, fell off the back of a truck somewhere between a mining site north of the town of Newman and the north-eastern parts of Perth. A search for the capsule is…