KARACHI   - Gold surged by Rs 300 to close at Rs 48,557 per 10 grams in the local market Saturday as its international price improved to $ 1,666 an ounce, market sources said.  According to Karachi Saraf Association official, tola (11.664 grams) price also increased by Rs 300 to Rs 56,600.  Silver closed higher at Rs 891.42 per 10 grams.