Take what you know about concrete: It's heavy, it's hard, it's cold. Now throw all of that out the window and take a gander at Dustin Faddis' Contribute Pen, which is made from engineered concrete blended into his own proprietary recipe.
Contribute has a very balanced feel. You will find it surprisingly light as it weighs 1.6 oz when housing the Signo-DX [a gel ink cartridge manufactured by Uni-ball]. Although smooth and polished, the concrete grips your hand, but feels soft. If you've touched a highly polished piece of marble, this would be a similar feel. Contribute takes on the ambient room temperature and will warm with your touch.
Pen enthusiast Faddis has not only tweaked his concrete blend, but developed a proprietary manufacturing technique. While there's understandably no video of his secret sauce, there is a neat clip showing how the cap closes:
Neodymium magnets embedded within the concrete enable that trick. And when the pen runs dry, you can insert refills from several different manufacturers (Cross, Pentel, Pilot, Uni-ball) by unscrewing the back cap.
Ready to buy yours? The Contribute starts off at $55 on Kickstarter. This one's gonna be a nail-biter—at press time there were six days left for Faddis to make the last 25% of his target of ten large.