The spelling of /s/ is <s> or <ce>. The /ʒ/ sound is spelled <ge>, <su> and <j> where it ocurs initially in the loan word jabot.
The contrast is between two fricatives, one voiceless and one voiced but fairly close in the mouth. The /ʒ/ sound may be troublesome for learners, since there are many languages which do not have a close equivalent. However, the contrast between the two is so rare that it will probably not be a problem.
The huge discrepancy in frequency, with /s/ nearly 100 times more common than /ʒ/, means that the figure for the mean density is only 0.1%. The set makes 8 semantic contrasts, a loading of 74%.
base beige Bruce Bruges closer closure lesser leisure loose luge looses luges Messrs measures person Persian persons Persians sabot jabot sabots jabots
John Higgins, Shaftesbury, July 2014.