From Guild Wars 2 Wiki
Brandstones can be found across the Domain of Istan at Brandstone Impact Sites. You need Brandstone Multitools to be able to mine it efficiently.
- In order to mine it, you must do the following:
- If you have it unlocked, use Impact Site Marker (skill 5) on the landing site.
- Use Extraction Beam (skill 3) to mine it. This can be done several times until the Brandstone gives no more loot. If you are too far from the Brandstone, you will have to approach it to pick up the loot from mining.
- As the Brandstone reaches 75%, 50%, and 25% HP, crystal shells break off. At 0% HP, the last shell will break off, revealing the core, and leaving only a few seconds to mine the site if you have not already fully mined it.