@misc{indiciae1cf18831970a,
  title = {Silver-bearing black calcite in western mining districts},
  author = {D. F. Hewett and A. S. Radtke},
  year = {1967},
  doi = {10.2113/gsecongeo.62.1.1},
  url = {https://pubs.usgs.gov/publication/70210850},
  note = {Source identifier: 70210850}
}