Per this story re the island “hobbit” people where they found stone tools dating to 800,000 years ago, if it 's “stone” how are you going to differentiate it age-wise from a random rock?
I believe they can date a rock based on the other fossils they find buried with it. Also, if there is carbon in or around the rock they could possibly do carbon dating.
Carbon dating only works to about 60,000 years. There are other radiometric dating measures that can be applied, though I don’t know which if any would be appropriate here.
This link indicates that these particular tools were dated by fission-track dating of layers of volcanic rocks above and below the site. Uranium in the rocks gradually undergoes radioactive decay, leaving tracks that accumulate since the last time the rock was molten. The density of fission tracks gives the age.
Potassium-Argon dating goes back 100,000 yrs and is specifically used to find the age of rocks. Stone tools are made of rocks. 
However, it will only give you the age of the rock itself, not when it was made into a tool. It also requires that there be volcanic deposits above and below the tools.
Also, because of the long half-life it is most useful for dating rocks more than 100,000 years old, and can date them back billions of years.
Mostly, artifacts are dated by where they’re found. Stratographic data can be calibrated using isotopic, magnetic, and tree-ring data. Use as tools can be dated by obsidian hydration and thermoluminescence. A good primer is here.
Wow. I’m just shocked to learn hobbits were real.
Presumably, the anthropologist buys some flowers, or maybe some candy, engages in a little small talk, then, when the moment is right, ask the stone tool if it wants to go to a movie, and maybe some dinner before…
If I remember correctly, a few days after the discovery of those ‘Hobbits’ they discovered a modern village nearby full of tiny people wearing T Shirts and trainers.
Something to do with ‘island miniaturization’
First they ask it out for coffee…
Then they ask if it’s going to be at AIA this year…
snort
I kill me.
If the stone is heated in a fire for some reason, many of the defects created by radiologic processes will “zero-out”. Thermoluminescence dating will pick up the radiation that the specimen had experience since it was last heated. According to the Wiki sunlight will also “zero out” the defects.
So a lose tool from a collection can no longer be dated, right? You need its environment to date it.
Really, the anthropologist should get drunk first, so that a stoned tool has a chance of having a personality that could match the stone tool.
Some dating is done by the style of human modification. If a certain kind of tool was known to be used in a certain era (and that was dated by various coorborating methods), then finding another in a reasonable location might be assumed to be of the same rough age.
Although I have seen some stone “tools” that look more like random rocks than tools, and I think defining those as tools is due to the mindset of the cataloger.
Yeah, anthropologists should have more common sense than to just date a random tool!
This is pretty much correct. A stone tool with no provenance doesn’t tell you anything except that once upon a time a human being made a tool.
wow, after a rough day at work, you made my day 
three words, three puns… …man, I love this place
I dated a stoned tool. I’m glad I got out!
But did you get your rocks off?