Congratulate on the find...
Judging from the images you have found a very interesting bone colored translucent Arkansas, usually when they are like this color they are very hard, very fine, very slow and have less light translucency... also you seem to have a fine Washita there.
how to clean your stones will depends on what you want to use them with, if you are planning to use them with oil, I would say just lap them and use dish soap to clean them preferably one with antibacterial since you will hone your razors on them, But if you are planning to hone with water which is my preference as it is faster and give sharper edge IMO, I would not recommend blindly boiling the stones especially the denes Hard translucent, as putting the stone in the hot water while the core of the stone is colder may fracture the stone or pulling the stone out of the water while it is still hot and leaving it to air cool will damage the stone too as the outside of the stone will cool faster than the core which will lead to fracture... To boil your stones you need to put them in a room temptation water then start to heat them to gentle simmer for very short period of time then turn of the heat and let them cool inside the hot water, this way is safer with porous stones like Washita’s but with the translucents and the true hard there will be always a chance that your stone might get damaged, believe me I learned this the hard way. There is a safer way to clean the stones, you can soak them in rubbing alcohol (isopropyl alcohol) for several days giving them a shake or two a day, I use 99.9% to soak any oily stone I get for 1-5 days depending on the stone and the level of accumulated dirt.
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( this washita was a jet balck when I got it, I brushed it then soaked it for a week you can even see how clean it is from inside thanks to that chip :) )
You can substitute the rubbing alcohol with car brakes cleaner/ degreaser it is very effective maybe better than the concentrated isopropyl alcohol, but I happen to have the alcohol in large quantity for other uses. Having said the above usually the dens stones need only wiping to clean them as they don’t soak oil.
After lapping you stones you will have to dress them properly to get them to perform the best for you, the best way to do so IMO for Arkansas stones is to sharpen a very hard steel knife or tool on them with heavy pressure but you need to be careful not to scratch to stone or injure yourself while doing so.... then you will have one of the finset stones on the world
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BTW, if you have a local lapidary in your area they can lap the stones initially for you then you can finish them by hand.
Happy Lapping :rofl2: