I felt below my feet a rock- bed foundation which nothing could shake. "The Adventure of Living" by John St. Loe Strachey

And she must ha' been a rock for me to give in to her in that. "The Complete Project Gutenberg Works of George Meredith" by George Meredith

She was as firm as a rock about it. "The Hollow of Her Hand" by George Barr McCutcheon