The resources you collect as you wander around Assassin’s Creed Valhalla will be how you upgrade your items, enhance your weapons and armor, and acquire money. A notable resource you may not find for a bit of time are opals. An opal is a rare material that will be harder to find, but you can provide them to traders who can trade exotic goods for them. These goods will prove more useful for you, so it’s worth your while to figure out how to find it reliably.
There are two ways to find opals. The basic way is to go raiding, fight against a horde, and then potentially loot it in the village or camp you attacked. You’ll have to look around a bit to grab it, and it’s never a guaranteed drop, so you don’t want to raid every village you encounter searching for opals. There’s an easier method.
The best way to find opals is to use your raven. You can call it by hitting the up button on your controller’s directional pad. When you summon it, have it hover in stationary mode by hitting the left trigger, and then observe the immediate area around you. Look for a stone with a cross-like symbol in the middle, pictured below. Place a marker on the waypoint.
When your raven locates it and places the marker, Eivor can run on foot to find it. Reaching these locations where you can find opals varies from taking quite a bit of time to rummaging around a deserted village. It’s always worth it when you bring in a massive load of opals to a trader and offer them over for some exotic goods you can’t get anywhere else.