  Averievite, Cu$_5$V$_2$O$_{10}$(CsCl), is an oxide mineral composed of
Cu$^{2+}$ kagome layers sandwiched by Cu$^{2+}$-V$^{5+}$ honeycomb layers. We
have synthesized this oxide and investigated its properties from ab initio
calculations along with susceptibility and specific heat measurements. The data
indicate a Curie-Weiss temperature of 185 K as well as long-range magnetic
order at 24 K due to the significant interlayer coupling from the honeycomb
copper ions. This order is suppressed by substituting these coppers by
isoelectronic zinc, suggesting that Zn-substituted averievite is a promising
spin liquid candidate. A further proposed substitution that replaces V$^{5+}$
by Ti$^{4+}$ not only dopes the material, but is predicted to give rise to a
two-dimensional electronic structure featuring Dirac crossings. As such,
averievite is an attractive platform for S=1/2 kagome physics with the
potential for realizing novel electronic states.
