We see needle-shaped ice crystals in soil often enough, but I've never seen them so fine, so long, and so dense. We'd had prolonged rain before the prolonged, gentle freeze that created what looked like scattered patches of wool on saturated sticks on the ground. This clump is growing out of a stick about 2 inches (5cm) in diameter.
I was mountain biking a favorite trail on Chuckanut Mountain in December, 2006 when these caught my eye.