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Powdered silica has long been used for the purification of nucleic acids in the laboratory. Silicate-rich, ordinary ocean beach sand was found to concentrate dissolved DNA from seawater over 10 000-fold, providing a rich, renewable, and easily accessible genetic library that is easy to harvest and inexpensive to process. We found an average of 29 µg ml -1 of cell-free DNA adsorbed to silicate-rich, wave-washed sand from 14 beaches bordering 9 seas around the world. The DNA from a reference beach was shotgun cloned, 3 107 399 nucleotides of anonymous, non-redundant sequence were analyzed, and 2571 genes were found; 2562 of these genes were new. The apparent complexity of sand DNA was greater than 1.4 × 10 11 nucleotides. About 90% of the sequences identified were from prokary- otes, 10% from eukaryotes, and 1% were viral. Sequences from all kingdoms of life were present. Over half the sequences came from new phylotypes, reflecting the novelty of this genetic reservoir.