These calculations result in ages for the Earth of 4.52 to 4.56 Ga. Probably the best value is 4.54 Ga, found by (Fouad) Tera using the congruency point of the four oldest conformable lead ores. Its value, which is known to within 1% or better, is consistent with the ages of meteorites, the ages of the oldest lunar samples, and the ages of the oldest Earth rocks.