The U.S. dollar posted good gains on foreign exchange markets yesterday, buoyed by a firming in Eurodollar interest rates and by short covering on some European currencies.

Gold closed in Zurich at $515.50 an ounce, up from $510.50 Wednesday, and at $516.50 in London, up from $510.50.

In New York gold was trading at $511.50 at the close, down from $514 Wednesday. The Comex settlement price was $509.60, down from $513.80. Silver closed at $13.125 an ounce compared with $13.20, and it settled on the Comex at $12.94 compared with $12.90.

In Tokyo the dollar made cautious gains to close at 232.65 yen, up from 230.90 Wednesday.

In London the pound inched up to $2.2858 from $2.2820.

But in Frankfurt the dollar added on to early gains to close at 1.7925 marks compared with 1.7815 Wednesday. It rose in Zurich to 1.66 Swiss francs from 1.6535, in Paris to 4.2020 francs from 4.1850, in Brussels to 29.585 Belgian francs from 29.345, in Amsterdam to 1.9805 guilders from 1.9755 and in Milan to 844.50 lira from 841.05.