a RFID tag (full name Radio Frequency Identification, data collection technology that uses electronic tags for storing data) works in a portion of the ultra high frequency (UHF) range.
the extraction of coal or its products from layers of rock by underground mining methods such as room-and-pillar mining and longwall mining.
Upper Silesian Coal Basin:
a coal basin in Silesia in Poland and the Czech Republic. The area contains a number of mineable resources including lead, silver and zinc; and resources of coal reach depths of 1000 metres below ground, approximately 70 billion tonnes of coal.