Emerald dust is a crafting component in The Witcher 3: Wild Hunt that is needed to craft the following items:

It can be found as random loot, guaranteed in a small red-glowing chest inside the nekker monster den east of Ursten, random drop from barghests, tangalores, noonwraiths and wraiths, or purchased from the following merchants:

• All armorers and blacksmiths, except the one at Ardaiso Quarry
• Armors and weapons merchants in Nilfgaardian Army Group 'Center' Camp
• Alchemist in the Crematory near Oxenfurt Gate
• Merchant in the boatyard south of Refugees' Camp
• Merchant at Calveit Watchtower
• Merchant at Coast of Wrecks
• Merchant in the shop in Gildorf
• Merchant in Putrid Grove
• Merchant in the market northwest of Tretogor Gate
• Merchant in Ursten
• Merchant by the road west of White Eagle Fort
• Merchant at the sawmill northeast of Rannvaig
• Merchant at the Isolated Hut on Hindarsfjall
• Merchant in Mohrin Village
• Merchant in Stacheier
• Ofieri merchant at Upper Mill

Emerald dust can also be obtained by dismantling: