When I first heard about stone paper, I imagined writing on hard sheets of limestone with a piece of chalk.

I got it 1/4 right. Stone paper is in fact made from limestone, along with calcium carbonate and HDPE plastic. But, it's as thin and flexible as a sheet of paper, and writing on it, in pen or pencil, is a breeze. (Admittedly, I haven't tried writing on it in chalk. It's probably wonderful.)
As you may have guessed, no trees are harmed in the making of stone paper. In fact, less waste is generated in creating this paper than regular paper. Replease 1 ton of regular paper with 1 ton of stone paper and you will save:
6 million BTU of energy
20 trees
167 lbs of solid waste
236 lbs of atmospheric emissions
and 7480 gallons of waste water.
Eco-friendly: check.
Wait, if this is made out of stone, will it last forever? Nope, it is completely biodegradable.
But can it be recycled? It sure can, just like any other paper.

Stone paper has some other convenient properties too. Not only is it chemically benign, it's naturally anti-bacterial. Great for doctor's offices, schools, and anywhere else lots of hands touch the same sheet of paper, especially during flu season.
It's also great for backpacks and purses, because it's tear resistant.
Finally, what I think is the coolest part, it's waterproof. Yes, waterproof paper. Sorry kids, you can't use the, "I dropped my homework in a puddle," excuse for this paper. In fact, I need to borrow a dog, it may even be, "The dog at my homework," resistant.
And at a price point of $3.00 - $3.80 each, a 5" x 7" notepad would be an affordable, eco-friendly gift for your employees or clients.