- For the castle see Dragonstone (castle)
- "The island itself was and is nothing. It had no gold or gems to lure Valyrian nobility, all it has is rock."
- ―Stannis Baratheon
Large amounts of dragonglass can be found on Dragonstone, but it isn't a precious or even particularly useful material, being too brittle to make weapons and too sharp to use in building. Otherwise, the only significant advantage of holding Dragonstone island is its strategic position, guarding the entrance to Blackwater Bay and King's Landing.
In the books
One of the few advantages the island itself possesses (besides its strategic location) is the active volcano known as the Dragonmont - possibly the only large active volcano in the Seven Kingdoms (though smaller thermal vents and hot springs are relatively common). Dragons prefer to nest in caves in the sides of volcanoes, being attracted to the heat. The ancient Valyrians first discovered dragons nesting in the string of volcanoes in Essos known as the Fourteen Fires. Dragonstone island was thus an ideal location for the Targaryens to raise and breed their surviving dragons. Some dragons were later raised in the massive Dragonpit built in King's Landing, but the main hatcheries remained on Dragonstone in volcanic tunnels.