From http://groundwork.sidereel.com/mixins Font Stack

font-stack

@mixin font-stack($primaryFont:"", $secondaryFont:"", $fallbackFonts:"Arial, Helvetica, Geneva, sans-serif") {
  /* might add inline-font-files() at some point */
  @if $secondaryFont != "" {
    font-family:#{$primaryFont}, #{$secondaryFont}, #{$fallbackFonts};
  } @else {
    @if $primaryFont != "" {
      font-family:#{$primaryFont}, #{$fallbackFonts};
    } @else {
      font-family:#{$fallbackFonts};
    }
  }
}