Description of Historic Place

Glacier Rock is a two-meter-high granite boulder. This spectacular and unusually rare granite boulder is located at McAdam Heritage Park in the Village of McAdam.

Heritage Value

Glacier Rock is designated a Local Historic Place for being a rare natural phenomenon. The Village of McAdam is known as the "Lakeland of New Brunswick" because of the many surrounding lakes and rivers gouged out by the glaciers southeastern advancement and receding 13,000 years ago. The village could just as appropriately been called "Rockland" as granite boulders were deposited everywhere in the area due to this same process. Originally located just north of the village, this very rare unusual composition of colourful circular granite melted together by extreme pressure and heat was discovered sitting among hundreds of gray granite boulders and has come to represent and symbolize the geological history of the area of and around McAdam. The presence of what is called "Pokiok" granite in the composition indicates that it may not have come from very far laterally, but the circular features known as ‘orbicules’ (from the Latin meaning circles), indicate that they were formed some 400 million years ago when rocks melted deep in the earth's crust and rose to the surface, solidified and subsequently broke off. These rocks were then carried and rolled round into the circular shape by moving glaciers, creating the spheroid composition. While considered rare, such spherical patterns have been seen in granite in other parts of the world. The formation has been described locally as a boulder “that looks like a bunch of stone masons got together and mortared a lot of small granite stones into one great blob”. The rock was moved from its original location to the McAdam Heritage Park.

Source: McAdam Village Office, Historic Places Files “Glacier Rock”

Character-Defining Elements

The character-defining elements relating to Glacier Rock are:
- approximate 2 metre height and weight of 30 tonnes;
- "patchwork quilt" motif of pink and buff coloured spherical patterns;
- outer rim of finely textured, light grey granite surrounding an inner core of dark sedimentary rock of the spherical patterns called ‘orbicules’;
- network of pink, coarse textured granite possibly of Pokiok granite, that separate each of the spheroids;
- in the sedimentary cores of the spheroids, the fibrous mineral sillimanite identified as aluminum and silica that forms only at temperatures above 500 degrees.