Yogo Sapphires

Our friends in Montana own a claim at the sapphire mine in Yogo Gulch. We spent Thursday of last week touring the mine area and sorting through some ore that was harvested the previous year. Ore is harvested and allowed to freeze over the winter so that it will split apart when it is tossed into the tumbler. Once tumbled and screened the sapphires are heavier than most of the surrounding rocks and will sink to the bottom and rest on the screen. The screen is then flipped and the sapphires sparkle in the sunlight as they lay on top of the rock pile... Well, if you shake the screen just right and then flip just right and have ore that actually has sapphires in it they will sparkle in the sun. We learned the techniques and found a few sparkles; but mostly we had fun.

Dave tumbles the ore and pours it onto the screen for sifting

Then we look...

and look...

and look some more...

The fruits of our labor... we ended up with one tiny stone large enough to cut but the rest were chips. The only value the chips have is as a novelty or, being a 9 on the Mohs scale of mineral hardness (diamonds are a 10), the sapphire chips once had value in the industrial market as an abrasive.
A few websites that have some information about the Yogo Gulch and the sapphires: http://www.geo.utexas.edu/courses/347K/redesign/gem_notes/Corundum/corundum_triple_frame.htm