Complex sentence: TJC sells a wide variety of gemstone jewellery, loose gemstones, watches, fashion jewellery and simulated gemstone pieces and they are one of just eight sightholders of the Tanzanite One mine.
Split into simpler sentences: TJC sells a wide variety of gemstone jewellery, loose gemstones, watches, fashion jewellery and simulated gemstone pieces. They are one of the eight sightholders of the Tanzanite One mine.