Final answer:
The oldest known mineral grain is a 4.4-billion-year-old zircon crystal found in an ancient sandstone. The age of this zircon grain was determined through uranium-lead dating, a method that measures the ratio of uranium to lead isotopes in the crystal. Zircon crystals are valuable for geochronology because they are present in various types of rocks, allowing scientists to determine the age of different rock formations on Earth.
Step-by-step explanation:
The oldest known mineral grain is a 4.4-billion-year-old zircon crystal found in an ancient sandstone. The age of this zircon grain was determined through uranium-lead dating, a method that measures the ratio of uranium to lead isotopes in the crystal. By comparing the ratio to the known half-life of uranium-lead decay, scientists can calculate the age of the crystal.
Zircon crystals are valuable for geochronology because they are present in various types of rocks, including igneous, metamorphic, and sedimentary rocks. This allows scientists to use zircon crystals to determine the age of different rock formations on Earth.
The discovery of the 4.4-billion-year-old zircon crystal provides evidence that the Earth's crust is at least that old. Based on this age, scientists estimate that the Earth itself is between 4.4 and 4.57 billion years old, which is the age of the solar system.