Complex sentence: In 2011,1.7 million tonnes had been produced, mostly by Greece (500,000 t), United States (375,000 t) and Turkey (220,000 t); however, no information for China--a leading producer--was available.
Split into simpler sentences: In 2011,1.7 million tonnes had been produced, mostly by Greece (500,000 t), United States (375,000 t) and Turkey (220,000 t). However, no information for China--a leading producer--was available.