We demonstrate efficient Raman lasing with ${\mathrm{CaF}}_2$ whispering-gallery-mode resonators. Continuous-wave emission threshold is shown to be possible below $1\mathrm{\mu }\mathrm{W}$ with a $5\mathrm{mm}$ cavity, which is to our knowledge orders of magnitude lower than in any other Raman source. Low-threshold lasing is made possible by the ultrahigh optical quality factor of the cavity, of the order of $Q=5\times {10}^{10}$ . Stokes components of up to the fifth order were observed at a pump power of $160\mathrm{\mu }\mathrm{W}$ , and up to the eighth order at $1\mathrm{mW}$ . A lasing threshold of $15\mathrm{\mu }\mathrm{W}$ was also observed in a $100\mathrm{\mu }\mathrm{m}$ ${\mathrm{CaF}}_2$ microcavity. Potential applications are discussed.