When you conquer the guardian, it will drop a key, which may be used to unlock the door beforehand. This is where the ore is. Depending on the number of creatures you killed, there will be many more stone. The rocks can be mined after before they disappear.
Another alternative comes in if you've got 50 Magic. It may only be cast after the rock was mined. This spell will turn the stone to some"Binding Stone". Pick this up and use it with the ore to get a"Strong Ore". Should you make a Complete armor set with this, the armor will last longer (see below)
All these armors degrade, such as Barrows armor. Alum can take 500 harm, or 700 with binding, gold may take 1000 damage, or 1300 with binding, and diamond can take 1500 damage, or even a massive 2000 with binding. As soon as they are degraded fully, you need to make some more from ores. To make these armors, you have to take the ores into a furnace, and this will turn them to chucks instead of bars. Then use them in an anvil with a hammer. Diamond armor provides 200 exp for each piece you create, gold provides 150 exp and alum provides 80 exp.
Check out https://www.rsgoldfast.com for more details.