Walter Industries Inc., a Tampa producer and exporter of metallurgical coal for the steel industry, doubled its net income in the third quarter, the company reported this week. "Our natural resources business generated outstanding results," said Michael Tokarz, Walter Industries' chairman. The company reported net income of $55-million, or 97 cents per diluted share, for the quarter ending Sept. 30, compared with $24.4-million, or 46 cents per diluted share, for the year-earlier quarter. Earnings would have been $1.27 per share if it weren't for a steep decline in Walter's financing and home-building unit due to the deteriorating market, and charges totaling $21.3-million. The Natural Resources & Sloss group had revenue of $322.2-million in the third quarter, a 61.2 percent increase.