Abstract It was pointed out in 1984 by Witten that strange quark matter (SQM) – matter made of up, down, and strange quarks (rather than just up and down, as are protons and neutrons) – might well be stable and the lowest energy state of matter. The reason is that it would be electrically neutral and have less Pauli-Principle repulsion. Binding would increase with numbers of quarks, and might not begin below thousands. It would have nuclear density. Neutron stars would be strange quark stars; and it might conceivably constitute dark matter. One way to detect ton-range SQM nuggets (SQNs) would be from seismic signals they would make passing through the Earth. We give a rough estimate on the relative advantage of attempting to detect SQNs on the Moon over Earth (about 50 times more detections).