  Quark clustering could occur in cold quark matter because of the strong
coupling between quarks at realistic baryon densities of compact stars.
Although one may still not be able to calculate this conjectured matter from
first principles, the inter-cluster interaction might be analogized to the
interaction between inert molecules. Cold quark matter would then crystallize
in a solid state if the inter-cluster potential is deep enough to trap the
clusters in the wells. We apply the Lennard-Jones potential to describe the
inter-cluster potential, and derive the equations of state, which are stiffer
than that derived in conventional models (e.g., MIT bag model). If quark stars
are composed of Lennard-Jones matter, they could have high maximum masses
($>2M_{\odot}$) as well as very low masses ($<10^{-3}M_{\odot}$). These
features could be tested by observations.
