An elaborate ark once belonging to the Goa'uld Sekhmet was among the artifacts that were acquired by a rogue NID sleeper cell in Los Angeles. The ark was adorned with the golden motif of Ra, the sun god, and had possibly been a gift to Sekhmet. In the corners were four scarabs which turned as a sort of combination lock to open the ark, and inside was an explosive device containing a ten pound block of naquadah.
Dr. Keffler had created Anna, a human-Goa'uld hybrid, in order to access the genetic memories of Sekhmet, but instead, Sekhmet emerged as a distinct personality and activated the naquadah bomb which threatened to wipe out all of Orange County. With only hours before detonation, Dr. Lee and Teal'c struggled to disarm the device, but the solution was found among the drawings that Anna had created to express the dark Goa'uld memories that she accessed in her mind. One of the sketches revealed the position of the scarabs to unlock the ark, and another showed the deactivation code necessary to stop the countdown with moments to spare.
On P4M-328, SG-1 discovered an identical Goa'uld naquadah bomb as an artifact in a museum. Sealed in a glass case and protected by a security system, the device could only be accessed by using a security card and code, but Vala activated the bomb to persuade the security guard to cooperate. Unable to disarm the device once it had been activated, Vala had less than an hour to use the power from the naquadah core to manually dial the stargate. Establishing a secure connection with the gate would completely deplete the power source and eliminate the risk that the bomb would detonate, and SG-1 succeeded in using the device to dial home from a planet without a DHD.
Cross Reference: Anna, Crystals, Dr. Keffler, Bill Lee, Manual Dial, Naquadah, P4M-328, Sekhmet
Episode Reference: Resurrection, Bad Guys