Phantom drive icon appearing on my Mac mini

• Exactly what macOS version is running on your Mac mini?

• If you double-click that desktop icon what is revealed? Is there data stored in that drive volume?

• Do you use Carbon Copy Cloner (CCC) on your Mac?

• If you launch CCC, do you find this drive volume listed as a destination for a CCC backup task?

• Maybe it is a forgotten volume or partition that was created at some point on your startup disk?

Launch Disk Utility and take a look at the drive volumes that are listed in the sidebar to the left.

• Do you see that volume listed there?

Disk Utility User Guide for Mac - Apple Support

If so, and if you don't need the volume, then you may simply delete it.

If your drive is APFS formatted and this is an APFS volume, then it should be easy to delete the volume itself without issue. If your drive is otherwise formatted, then removing the volume may require repartitioning the drive.

Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support

Does this drive icon have a name? Perhaps something similar to xxxxxxx.img?

What happens when you click the icon and press command-E (⌘E) to eject it?

Good computing, my friend.

Apparently an errantly created (?) drive volume.

Thank you for updating us. 👍🏽