Spiaggia dei Maronti, Ischia

What Seaglassmap found here

Two kilometres of dark volcanic sand and small stones under the cliffs of Barano, and the beach that collectors staying over in Sorrento are told to take the ferry for. Bus 5 from Ischia Porto drops you at one end, or you can come by water taxi from Sant'Angelo. The coarse volcanic grit does the tumbling here. What people report is how much there is rather than anything unusual, so give yourself time and walk the whole length.