Talc has the composition of Mg₃Si₄O₁₀(OH)₂ and is a soft flaky white mineral. The talc-bearing rocks in this area are white, light gray, or light green and usually are irregularly stained yellow-brown by the weathering of an iron-bearing mineral that occurs with the talc. Because of its extremely soft nature, the talc does not form prominent rock exposures. As shown by the figure, the talc can be most easily observed along the shore of Sterling Pond, south of the Green Mountain Club cabin, or along the trail to Smugglers Notch near the top of the first rise from the pond. Here the talc is exposed in the trail as low, rounded, slippery knobs of “messy looking” yellow-brown rock. As part of the pond is underlain by talc, it is probable that the softness of the talc was a factor in the differential erosion of the basin by the continental glacier. The talc is believed to have originated by the alteration of a body of _ultramafic_ igneous rock, which is characterized by having a low silica content and a high magnesium content. Sometime during the mountain-building period, the ultramafic igneous rock invaded the pre-existing rocks from an unknown source within the earth’s crust. It is believed that at a later date the original minerals in the igneous rock were altered to talc and other minerals by the action of hot ascending solutions composed principally of water. [Illustration: Figure 8. Sketchmap showing the location of the talc-bearing rocks at Sterling Pond.] MAP OF THE STERLING POND AREA FOREST BOUNDARY Green Mountain Club cabin STERLING POND To Smugglers Notch EXPLANATION Talc-bearing rock Solid areas are positions of exposures Postulated boundary of talc body beneath pond Trail To Spruce Peak From report by A. H. Chidester The Long Trail passes by Sterling Pond, where the Green Mountain Club has erected a small cabin overlooking the pond. Figure 9 is the picturesque view of Mount Mansfield taken from the cabin. _Smugglers Notch_ All of the rocks exposed at Smugglers Notch (Figure 10) are the mica-albite-quartz schist which locally contains garnet. The large rock boulders in the Notch were derived from the cliffs forming the walls of the Notch. The gradual processes of weathering and breaking up by freezing cause large slabs of the rock to become loose and eventually break off the cliff faces to careen down the mountainside to the valley below, just as King Rock did within historical time. At the north end of the Notch, the large accumulations of such boulders form a _talus slope_, the name for rock accumulations at the base of a cliff. The irregular stacking of these rocks have formed Smugglers Cave. Smaller openings extend further back under the “rock pile” to where the ground is considerably colder and where the heavier cold air has sunk. Drafts of this air escaping at the foot of the talus is noticeably cool.