I own these stones, having purchased them a few years ago from YMI, and washing and oiling will definately improve the "feel" of the dark stones (the light "candy apple" green stones are smooth glass, so don't need oiling, but a wash couldn't hurt). The dark "seaweed" green stones come preoiled, but since I didn't know what oil was used, I felt it prudent to give them a good wash; I then oiled them with my oil of choice (mineral) since this is an edible oil that doesn't easily evaporate and doesn't get gummy or sticky (I also use mineral oil on my Yunzi stones to good effect). If you just wash and don't oil the dark stones they will look a bit "dry" and feel somewhat rough to the touch, but after the mineral oil bath (remember, just a few drops in a ziplock bag and a wipedown with a towel to remove the excess) you will find they have a velvety smoothness in appearance as well as touch!!
Now, having said all that, I should mention that the pictures don't quite capture the true colors of these stones--the "candy apple" green stones are quite intense--so "easy on the eyes" they ain't. I had originally ordered these stones to go with a YMI bamboo board, but I found the "seaweed" color of the dark stones did not have sufficient contrast against the (relatively) dark bamboo (I then got jade-colored Yunzi stones which look great on the bamboo). Similarly, these stones didn't work with a katsura board due to its darker hue, and additionally the stones were an uncomfortable fit on the Japanese grid (most Japanese stones are 21.5mm or smaller, while these Korean stones are 22mm--half a mm matters when they are laid end-to-end across a board!). I finally found a "mate" for the stones in a 2 in. Korean agathis wood board from Yutopian (discounted due to slightly dented corner: https://www.yutopian.com/yutop/cat?product=TK110-D&category=T) as the beige-colored lacquer "wash" provides just the right amount of contrast with the stones, and the stones fit perfectly on the Korean grid.
Good luck with the stones and enjoy their antibacterial qualities courtesy of the "nano-silver" technology!
-- EdLee.)
