If you are looking for a locket for a mangalsutra, then buy such a light gold pendant on an oval shape. It has traditional work with small stones.
If you are looking for a locket for daily wear, then choose a heart-shaped gold pendant in 2-3 grams. In the photo, it is on two layers, but buy it in a single design.
If the mangalsutra chain is light, then you can buy such a light gold locket design on 2 grams.
If you want a solid and heavy gold locket, then this gold locket on leaf-eyeball will give a very great look. You can buy it in round designs.