I was given the stones above as a child by my grandmother. I don’t know where she got them, but she was from New York state. She called them “Indian paint pots.” (See, for example, Garvies Point concretions). The stones are hematite concretions used by Native Americans to paint their faces. The blunt end of the stone in the upper left could be rubbed in the bowl of another stone with water (we used saliva as kids, of course). A reddish paste was produced because hematite concretions are not particularly hard (which is why they make a red streak in the streak test).
Because of their high density, large hematite concretions have been used since prehistoric times for tools, like breaking bones. This appears to be a Native American tool, found in Missouri, that was made from a hematite concretion.
Thanks to many people for the photos: Aaron, Adam, Amine, Barry, Ben, Benjamin, Besik, Bob, Brad, Bruce, Cary, Cassiano, Christine, Danny, Dave, Donna, Dogsgrey, Ed, Elizabeth, Eric, Frank, Gary, Greg, Harold, Hassanat, Isabelle, Jack, Janet, Jason, Jean, Jeff, Jerry, Joe, Joel, John, Jonathan, Jordan, Judy, Julia, Kate, Ken, Kortnie, Larry, Lori, Lou, Mark, Mason, Matthew, Micah, Michael, Monir, Patrick, Paul, Rachid, Rainer, Richard, Rob, Robert, Robin, Ron, Scott, Sean, Senol, Søren, Theresa, Thomas, Tim, Tom, Toby, Warwick, and Wayne.