The Geode is a rare consumable dropped by Granite-themed enemies with a 5*1/20 (5%) chance. Geodes can be thrown with the ⚒ Use / Attack button, causing them to drop two types of gems upon impact with blocks. The amount of gems varies from 3 to 6.
On average, the resulting contents of the Geode are worth 154 (3080% of its sell price) and a minimum of 3375 (675% of its sell price), meaning it is always better to crack them open than to sell them straight.
This profit can be further increased by converting the contents to Stained Glass, which is worth about 10 times more than the gem ingredients and only requires the addition of 10 Sand Blocks per gem. This brings the average sell value of the Geode to 810 (16200% of its sell price).
However, Diamonds cannot be turned into Stained Glass, and as such, are most profitable being sold directly. Using this method, this brings the minimum value of a Geode to 390 (7800% of its sell price) in the event that it drops exactly 3 Diamonds and 3 of any other gem. The maximum value is 12 (24000% of its sell price) when it drops 6 gems each of two types that are not Diamond.
With these values in mind, the Geode drop adds the following value to every Granite-themed enemy kill:
25 when selling the Geode as-is
770 when opening the Geode and selling the gems straight