Enrique Marroquin has been a goldsmith for 35 years. For the past six, he has worked at Tiny Jewel Box in Washington, D.C., where estate and antique jewelry is a big draw. Marroquin says new advances in technology make it possible to better repair old heirlooms.JCK: What’s your most indispensable tool—hand or mechanical?Enrique Marroquin: The laser. The laser is mainly to fix platinum. It replaces a torch for working with platinum, because you cannot repair platinum pieces with a torch. That’s why platinum often used to be repaired with white gold.Welding platinum to platinum, you can’t do with a torch. The metal is too hard—you would have to get the torch so hot it would damage the stones, even diamonds. With the laser, you can work very close to the stones.Previous repairs on estate jewelry are something you always have to be very careful with—they fixed some things wi