Estabrook Park

Estabrook Park, along the Milwaukee River in Milwaukee, Wisconsin, is a genuinely famous mineral locality among collectors — and it's a city park today, not a working quarry. In the 1960s, the site (also known historically as Berthlet or the Milwaukee Cement Quarry) produced spectacular millerite specimens: sprays of lustrous, brassy millerite crystals growing inside calcite-lined geodes and vugs in the Devonian-age Milwaukee Formation dolostone, exposed where the bedrock had been quarried for cement. Those 1960s-era specimens are still prized by mineral collectors and museums today. The quarrying and the collecting window are both long over — this is now a public park with river-cut dolostone outcrops visible on the descent to the water, and collecting is not permitted. Worth a dossier for its history and identification value, not as a place to dig.

Estabrook Park is in the city of Milwaukee, Milwaukee County, Wisconsin, along the Milwaukee River. It's a developed city park with normal park access (roads, trails, parking).

Not applicable — collecting is prohibited (see below). Historically, the millerite came from geode/vug cavities in dolostone bedrock exposed by the former cement quarry operation on the site.

Estabrook Park is a Milwaukee County/City park, and the historic quarry ground here is now developed parkland where collecting is not permitted — sources describing the locality explicitly note it as "extinct" for collecting purposes, now that the site is a city park. If you want a millerite specimen from Estabrook Park, the path is buying an existing specimen from a mineral dealer or museum, not digging one yourself.