The Copper Pan is a tool. It can be used to collect ore and other items from different water sources.
You can obtain it in a few different ways. By completing the Fish Tank Bundle, purchasing the “Panning” option on the Joja Community Development Form for 20,000g, or in a cutscene with Willy that is triggered by traveling to the waterfall after the boulder is removed.
To pan for minerals, look for shimmering lights in any water source. Get near one, and use your Copper Pan to collect minerals or ore from that spot.
The Copper Pan cannot be sold.