This is indeed another glacial erratic, just like the Big Rock. Whether it was originally a piece of the larger house-sized chunk across the highway, or perhaps just another lonely quartzite boulder along for a ride on the same glacier/ice sheet thousands of years ago, is unclear. What is certain is that this is another glacial erratic and part of the Foothills Erratics Train: one of thousands of such boulders strewn across the Alberta landscape--an ancient geological record of the last Alberta Ice Age. You can read all about them at the famous Big Rock across the highway, or visit the links below!
Please replace securely as found.
http://www3.telus.net/lejgeology/etrain/
http://basementgeographer.com/glacial-erratics/