Banjo Cm chord (Double C)C minor on the 5-string banjo: 0 0 0 1, and 6 more shapes

Frets, string 4 to string 1: 0 0 0 1 (open position)

1. String 4 (C): open, C
2. String 3 (G): open, G
3. String 2 (C): open, C
4. String 1 (D): 1st fret, index finger, E♭
5. String 5, the short g: open, G, in the chord

Sounds: C G C E♭  ·  Cm is C, E♭, G (1 · ♭3 · 5)

Found in: C dorian (i), G minor (iv), C minor (i), B♭ major (ii), E♭ major (vi), A♭ major (iii)

The 5th string: the short g is the 5th of Cm, so let it ring.

Double C tuning: gCGCD, the short 5th string first, then strings 4 to 1.