Tesla CEO Musk lashed out at Apple during a conference call on his company’s quarterly earnings.

Musk said that Apple uses more cobalt in its batteries than Tesla, suggesting that they are almost entirely composed of cobalt, whereas his company’s batteries contain only about two percent of the element.

Cobalt is a key element for the production of batteries, which power not only all modern electronics, but also electric vehicles. In recent years, the media and human rights activists have drawn attention to the problem of obtaining a chemical element. 60 percent of this metal is mined in the Democratic Republic of the Congo. Cobalt mining violates working conditions and human rights, children work in the mines.