Rudy,
I've been there. To get started, take I-70 to the Wolcott exit and go north to the intersection with US hwy 6. Turn left and look for the sign to get you to Hwy 131. Take that quite a distance til you reach State Bridge, the bridge that crosses the Colorado River. Just across the bridge is CR1, turn right and proceed til you can see that you're going to cross the Colorado again. Just before that bridge, there's a parking lot on your left right next to the railroad tracks. Park there and walk across the bridge. Just across the bridge is a faint old road on your right. That runs right along the Colorado and if the river is in flood, you might have to hike to the destination along the ridge above you. And if it's late spring to summer, wear LOTS of deet...the ticks are BAD. (Actually, you can see your destination across the Colorado when you're on CR 1.)
The collecting spot is an old quarry and the old road across the bridge on CR1 is the old road to the quarry. Here's the coordinates for the old quarry. 39.876576 -106.631143.
I found some pyrite there, but a friend of mine who'd been there before came away with some nice pyrite balls.
Good Luck.