Here are some of the photos from my first walk around the Ross Marble Quarry. They're from the quarry area you reach at the end of the Imerys Trail. It's a pretty big area, and has obviously been used pretty extensively by mountain bikers, even before being fixed up by the Ijams folks.
Quarry floor:
View up one of the smaller ramps along the quarry's edge:
Quarry's edge seen from a distance:
Some of the slightly scarier ramps:
Couple more ramps up the side:
Long trail on the quarry floor:
Smaller jumps on the quarry floor:
Undeveloped trail going into the work area:
This is the view from the top of the scarier downhills:
Another view from the top of the quarry wall:
Good overview of the trails: