Thanks so much for telling me about that thread. You are right. That one picture does look just like my eggs! I've written to the person who posted it, but it looks like she's still a Newbie and hasn't posted for a long time. I hope her chicken didn't die of a bad disease and discourage her... I think I'll send my pictures to the local extension agent, too.
These pictures are of an egg that has abnormally passed through the shell gland where the eggshell is deposited. Ocassionally eggs will remain too long or not long enough and get an abnormally pigmented or chalky shell, such as these pictures show. Hens either coming into production or going out of production are more prone to this, but it can occur any time -- one of those quirks of Mother Nature. . . .