Dan Boyd has an excellent article in the Idaho State Journal on Borah:
Borah Peak on Mount Borah is Idaho's offering to the gods and the state's tallest point. To be precise, it's a 12,662-foot-high sedimentary sentinel that rises abruptly from the Lost River Valley floor near Mackay.
"That's what young mountains look like," said Paul Link, Idaho State University geology professor. "It's an actively uplifting range on an actively extending fault. That's why it's so steep."
There's nothing forgiving about the hike up Borah Peak.
What looks to be 15 minutes away melts into more than an hour as steep rocky slopes challenge the balance and willpower of even the most zealous mountaineer.
Anyone who suffers from vertigo might want to choose another hike - Borah's sheer vertical exposure would make even a mountain goat a bit queasy.
The key is to look for small rock cairns, and make sure you have good hand and footholds before scrambling your way up.
Link said most of the rock on Borah is limestone, dolomite and quartzite - sharp protruding rocks that offer good holds but which can come loose rather easily.