This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Katana showing alternating layers. Katana Showing alternating layers of hardenability In this photo lighter colored layers have higher carbon content than the darker layers In reality which layer is lighter or darker depends on the angle it is viewed from compared to the lighting Visible on the right hand side of the photo is the