Cursed, Blessed, and Mythic Tools
The level 6 and 7 tools come from within the Mines, in the northeast corner of the valley. You will need to have all 6 of your standard tools upgraded to Mythril before the next set of tools will appear.
You will also need to unlock the 3rd Mine at the excavation site to find the tools. The tools will be found randomly hidden in the dirt on specific floors. When you find a new tool it will be in it's cursed form. You will need to dig in the ground using your Hoe until you get lucky and you find one. If you equip the cursed tools in your red Tool slot of your rucksack you can not remove it! The only way to remove the tool is to get it decursed. Using a cursed tool will quickly drain your stamina.
Cursed Tools, mine levels
Floor 24, 35, 48, 52, 68, 71, 87, 99, 106, 118, 124, 135, 142, 153, 162, 178, 185, and 197.
Removing the curse from a tool is fairly painless but it can be expensive. Call the Church via your telephone and talk to the priest. He will remove the curse on any item for a 100,000 G fee. Once the curse has been removed you can use the tool in it's Blessed form. The second way to remove the curse is to have the 4th Mine unlocked and collect all 9 of the colored Wonderful Stones. When you get the last stone the Goddess will appear and she may ask if one of your wishes is to decurse a tool.
When you have all 6 of the cursed tools and you have changed them into their Blessed form, the Mythic Stones will appear in the 3rd Mine. These special jewels are randomly hidden in the rocks that you will need to smash with your hammer. Finding a Mythic ore will allow you to upgrade past the Blessed tools, but you must use your existing Mystril tools for the conversion.
Mythic Stones, mine levels
From floor 0 to floor 255, on any floor that ends in 0 (120, 230, etc).
From floor 256 to floor 999, on any floor that ends in 5 (455, 625, etc).
Take the special stone and call Gray on your telephone. He will charge you 50,000 G to convert your level 5 (Mystril) tool into the level 7 one. The Mythic level is the last stage in your tool upgrades. You can only have 1 Mythic Stone at a time, so don't bother trying to dig for more once you have one in your inventory.