While Marilyn Monroe maintained “diamonds are a girl’s best friend,” a pioneer woman would have been delighted to get hitched with a “prairie-diamond ring.” Until recently, I’d never heard the term before. However, thanks to Empire Mine blacksmith Bill Blount, now I know what it is, how it’s made and why it remains a robust symbol of romance on the prairie. Wearing his traditional leather apron, Bill welcomed me to the old blacksmith shop. For the last six years, he’s been a volunteer “smithy,” greeting visitors from all over the world — and telling them about the prairie-diamond ring. “Now, …