  The r-mode instability, believed to limit the rotation speed of compact
stars, can provide empirical confirmation for the existence of stable
deconfined phases of quark matter that are predicted by weak coupling
calculations in Quantum Chromodynamics. We construct a model for strange quark
stars as heavy as 2 solar masses that are made of superconducting quark matter
in the bulk and a thin crystalline quark matter crust. This crystalline quark
crust is sufficiently robust to withstand r-mode heating and viscous rubbing
for realistic mode amplitudes O(10^{-2}), unlike a crust made of neutron-rich
nuclei. The dissipation provided by viscous rubbing at the core-crust boundary
is both necessary and sufficient to obtain stable rotation speeds that are
consistent with the majority of rapidly spinning pulsars in low mass X-ray
binaries. Our analysis implies that while bare strange stars are ruled out by
the existence of rapidly spinning pulsars, a strange star with a quark matter
crust is a distinct possibility.
