Complex sentence: He began to work under his father but disliked working for De Beers, so he established his own firm, Industrial Diamond Company, exploiting the niche market for industrial diamonds, took over his father's dealer business in 1949 and later expanded into mining.
Split into simpler sentences: He began to work under his father but disliked working for De Beers, so he established his own firm, Industrial Diamond Company, exploiting the niche market for industrial diamonds. He took over his father's dealer business in 1949 and later expanded into mining.