It feels like New Jersey is famous for two things for the most part in the mineral world:

Trap Rock minerals and the Franklin and Sterling mines, the latter two being ore-bodies within the wider Franklin Marble rock unit.

Here, we have a nice ~4.8cm Corundum var Sapphire crystal (there's a second, less showy one out of view) from a mine just down the road from franklin: the Lime Crest Quarry. Yes, New Jersey has produced some great Corundum specimens. Ruby can also be found here, along with blue or purple sapphires.

Lime Crest Quarry, Franklin Marble, Sparta Township, Sussex County,

New Jersey, USA