spade, trowel
鑱 centers on a digging or scooping tool: a spade or trowel. Both meanings refer to a metal blade used for moving earth or applying material.
鑱 combines 金 (metal) with 毚, which likely contributes the sound and may relate to a sharp or pointed idea. The exact historical development of 毚 is uncertain.
The left side 金 (metal) shows the material, and the right side 毚 looks like a complex tool with a blade. Picture a metal spade with an ornate handle: 鑱 is a trowel.
For サン, imagine using a spade in the sun: sun -> サン, and the metal blade glints as you dig.