Some treasure within the dungeon can be found only by mining it out of the walls. Many rich strikes exist within each level, but must be found and mined. Quartz veins are the richest, yielding the most metals and gems, but magma veins will have some hoards hidden within.
Mining is rather difficult without a pick or shovel. Picks and shovels have an additional magical ability expressed as ‘(+#)’. The higher the number, the better the magical digging ability of the tool. A pick or shovel also has plusses to hit and damage, and can be used as a weapon, because, in fact, it is one.
When a vein of quartz or magma is located, the character may wield his pick or shovel and begin digging out a section. When that section is removed, he can locate another section of the vein and begin the process again. Since granite rock is much harder to dig through, it is much faster to follow the vein exactly and dig around the granite. Eventually, it becomes easier to simply kill monsters and discover items in the dungeon to sell, than to walk around digging for treasure. But, early on, mineral veins can be a wonderful source of easy treasure.
If the character has a scroll, staff, or spell of treasure location, they can immediately locate all strikes of treasure within a vein shown on the screen. This makes mining much easier and more profitable.
Note that a character with high strength and/or a heavy weapon does not need a shovel/pick to dig, but even the strongest character will benefit from a pick if trying to dig through a granite wall.
It is sometimes possible to get a character trapped within the dungeon by using various magical spells and items. So it can be a good idea to always carry some kind of digging tool, even when you are not planning on tunneling for treasure.
There are rumors of certain incredibly profitable rooms buried deep in the dungeon and completely surrounded by permanent rock and granite walls, requiring a digging implement or magical means to enter. The same rumors imply that these rooms are guarded by incredibly powerful monsters, so beware!