... I would strongly recomment the advise NOT to use acidic solutions for a simple cleaning of the sapphire as mentioned above. In addition, I would propose to support the cleaning steps by using an ultrasonic bath, eventually with some soft cleaning agents. Check suppier such as Dr. Stamm for suited agents (http://www.dr-stamm.de/produkte/index.html). I would try to use an agent that is routinely used for medical devices, as those usually contain only organic materials (such as Stammopur24 or stammopur db, check http://www.dr-stamm.de/pinf/ST24_81148de-7_STAMM.pdf and http://www.dr-stamm.de/pinf/DB_%2081048de-9_STAMM.pdf, sorry, those pages are only in german :-( ). Hope this helps, Dirk
In addition, if it is necessary to use any acid (as sometime it is necessary) then use week acid such as acidic acid, citric acid, phosphoric acid or their mixture. do not use H2SO4 in any way, certainly it will/can spoil fine polished surface as Sir K. Sreenivas already mentioned.