  Quark nuggets are a candidate for dark matter consistent with the Standard
Model. Previous models of quark nuggets have investigated properties arising
from their being composed of strange, up, and down quarks and have not included
any effects caused by their self-magnetic field. However, Tatsumi found that
the core of a magnetar star may be a quark nugget in a ferromagnetic state with
core magnetic field B between $10^{ 11}$ T and $10^{ 13}$ T. We apply
Tatsumi$'$s result to quark-nugget dark-matter and report results on
aggregation of magnetized quark nuggets (MQNs) after formation from the
quark-gluon plasma until expansion of the universe freezes out the mass
distribution to include $10^{ -24}$ kg to $10^{ 14}$ kg. Aggregation overcomes
weak-interaction decay. Computed mass distributions show MQNs are consistent
with requirements for dark matter and indicate that geologic detectors (craters
in peat bogs) and space-based detectors (satellites measuring radio-frequency
emissions after passage through normal matter) should be able to detect MQN
dark matter. Null and positive observations narrow the range of a key parameter
B to between $10^{ 11}$ T and 3 $10^{ 13}$ T.
