Zolurket remains abandoned for two reasons: the lack of worthwhile ores and minerals, and the presence of undead predators. The types of undead that lurk in the mines are unknown. There are rumors that Zolurket was abandoned before its wealth was depleted,12 and a mining company based in the city of Katapesh is attempting to reopen them.3
Founded over 2,000 years ago by dwarven prospectors, Tar-Urkatha was among the most prosperous halls in northern Garund, a jewel in the crown of dwarven architecture. It began as a small mining camp teasing reluctant platinum from the peak's hard stone, but in 2652 AR the miners discovered a massive vein of the precious metal.
As the dwarves plunged steadily downward extracting ore, they expanded the mining shafts and natural caves into grand, sweeping halls that became the envy of rulers both dwarven and otherwise. More workers were repeatedly brought to help, and soon resorted to recruiting inexperienced miners. For many centuries Tar-Urkatha made many lucky dwarves rich.
Then disaster struck. In the deeper pits, the novice miners found that the deepest veins of precious metal led through soft, chalky black rock that crumbled like old bone. The excavating was too easy for the greedy miners, unaware that it was a vast deposit of lazurite, a dangerous necromantically infused material known also as "marrowstone". With their greed came carelessness, and a hastily dug shaft collapsed, trapping a large mining team deep under huge volumes of rock.
For weeks, the dwarves labored to escape, but hunger, thirst, and hopelessness set in. Several dwarves committed perhaps the most heinous of blasphemies by eating their fallen brothers, and these unfortunates put to death by their fellow prisoners for their desperate act of cannibalism.
Soon, however, the lazurite that surrounded their corpses worked upon them and raised them as powerful ghouls that attacked the living survivors, who in turn rose as ghouls themselves. When the rescue team finally managed to bore an escape shaft into the blocked section, they instead found a small army of hungry undead. The dwarven ghouls slaughtered the rescue team, and the swift process of decay began.
The ghoul plague rose from the deepest pits like waters flooding a cave. The dwarves were caught off guard by the ferocious assault, and by 4121 AR realized that they were losing the Ghoulwar. They fled the mines in a mass exodus and locked their shame behind them.4
Paizo published a major article about the Zolurket Mines in Chapter 6 of Dungeons of Golarion.
For additional as-yet unincorporated sources about this subject, see the Meta page.