Same as ruby, I just soak in dark crystal cleaner, then quick qtip scrub and iso dunk water rinse paper towel dry.
OR, I torch clean right in the banger.
$290 USD? Is it 19mm and 18.5mm tall, or 18.5mm wide and 19mm tall? That much better than a GG 19mm ruby? (I have one of the 19mm ones before he changed to 18mm ...)
It's on sale!
The real value is with that 24mmX20mm! It's 18.5mmX19mm, but I haven't tried putting it in a 3mm sidewall banger yet, but will try once I get one soon.
I like sapphire better than ruby, and although the Greek ruby (I have a BaioT it's identical) is pretty damn amazing (comparing size/weight) especially for the price (and even just in general), they aren't as good BUT remember I use a torch exclusively so retention times are important to me. With an enail/coil it likely doesn't even matter?
BTW if you ever want to sell your 19mm Greek Sapphire (and make money) let me know!