York Haven Diabase

[2] It plays an important role in United States history as the diabase outcrops were useful barriers in the union's strategy against the confederates at the Battle of Gettysburg.

The York Haven Diabase began as one of many trough-like basins, which stretched from what is today northern New Jersey towards the northernmost tip of Virginia.

These basins opened during the Mesozoic Era along the eastern continental margin of North America and created areas for sediments and lava flows to settle.

It has a primary composition of amphibole and clinopyroxene, with abundant quartz and k-feldspar, some biotite, zircon, and apatite, and minor/trace amounts of chalcopyrite and galena.

[6] These counties include Adams, Berks, Buck, Chester, Cumberland, Dauphin, Lancaster, Lebanon, Lehigh, Montgomery, and as previously stated, York.