Because the story indicated by the Mithril Cube stated that the gold mine was most likely near this ancient Black Night Spirit Temple, and the gold ore Shade had picked up downstream bore markings indicating that the mine was very close to the upstream river channel, the two left the cliff and searched the surrounding area carefully.
Neither of them possessed any Thaumaturgy specifically meant for prospecting mineral deposits. For example, Ore Perception—a patch of land containing mineral deposits had a small chance of turning red, but unless one had mastered the Thaumaturgy deeply, it was very likely to give false results; Treasure Detection—chests, soil, and cabinets containing treasures would show white glimmers, but one had to be careful, as those treasures might already have owners; Money Rat Sense—greatly enhanced one's sensitivity to wealth, but the deeper one's mastery, the more one disliked cats.
Fortunately, as the Witch who held the "Earth" seat, Miss Benanis possessed an exceptionally strong ability to sense the earth.
After leaving the cave with Shade, she used Thaumaturgy to sense the surroundings, but found nothing at all.
Standing together in the Cedar Forest and watching Miss Benanis withdraw the "ruby" she had used as a casting medium from the snow, Shade thought that was only natural:
"Since it was worthy of being recorded by the Mithril Cube left behind by that Guardian, this matter must involve the supernatural. Perhaps some force has hidden the gold mine. Let's try looking for it another way."
So the two first led the horses over from the riverbank, then dug into the ground to determine what lay beneath the soil. This method was extremely time-consuming and inefficient. But neither Miss Benanis nor Shade was particularly attached to finding the gold mine. Shade even felt that if they really did