Cobalt canyon in the side of a mountain. The firm Calera Mining Company started production at the site. The stable form of cobalt is produced in supernovas through the r-process. It comprises 0.0029% of the Earth's crust. Free cobalt (the native metal) is not found on Earth because of the oxygen in the atmosphere and the chlorine in the ocean. Both are abundant enough in the upper layers of the Earth's crust to prevent native metal cobalt from forming. Except as recently delivered in meteoric iron, pure cobalt in native metal form is unknown on Earth. The element has a medium
Cobalt stable cobalt isotope and the only isotope that exists naturally on Earth. Twenty-two radioisotopes have been characterized; the most stable, Co has a half-life of 5.2714 years, and Co has a half-life of 271.8 days, Co a half-life of 77.27 days, and Co a half-life of 70.86 days. All the other radioactive isotopes of cobalt have half-lives shorter than 18 hours, and in most cases shorter than 1 second. This element also has 4 meta states, all of which have half-lives shorter than 15 minutes. The isotopes of cobalt range in atomic weight from 50 u (Co) to 73 u