The Stone Sword is a melee weapon that provides 15 damage points.
You can create it in your Crafting Menu (default key "Q") or at Crafting Tables (that still exist in older worlds created before September 2015), but only after unlocking the according crafting recipe by crafting (or taking) a Wood Sword made from Wood/Logs and Vines To craft one Stone Sword, you'll need
- 3 (blocks of) Stone mined from Caves, Mountains or the Fossil layer underground close to the surface, which requires at least a Wood Mining Cell
- 3 Bones, obtained from many Creatures like Pigsies, either by killing or harvesting from them if they are Pets, or can also be extracted from Fossils in a Processor
- 2 Wood Rods made of any kind of Wood or Logs in a Processor
- 1 Twine, made from Vines in a Processor
Crafting/taking a Stone Sword is the unlocking requirement for the crafting-recipe for the Obsidian Sword.
Very, very rarely you might still be able to find an (already crafted) Stone Sword in an Obsidian Treasure Chest on the Stalactite layer underground.
To use the new sword you must right-click on it in the inventory which will then place it into the weapon-slot next to your character's portrait and exchange any formerly equipped weapons. Afterwards you can switch between weapon-mode, tool-mode and harvest-mode with TAB (default key).
Whenever you hit a creature with a sword, the weapon will lose a bit of durability until it falls apart completely. The durability is indicated by a bar over the icon of the sword - in your equipment slot next to your character's portrait as well as on the main screen visible over the weapon slot. You might want to be prepared and take a new sword with you if your current one already hasn't much durability left!