Pirongia's many peaks are basaltic cones created by successive volcanic eruptions between the late Pliocene and early Pleistocene, about 2.5 million years ago.

[5] Kahupekapeka searched the bush on Pirongia for rongoā rākau (medicinal plants) to heal her body, which was afflicted by the miscarriage of her unborn child with Uenga.

It is a mainly basaltic volcano, though andesite dykes form the peaks of Wharauroa, Mahaukura, Tirohanga, Pirongia Summit and The Cone.

To the west it merges into the highland terrain of the Karioi horst block and in the east it arises above the Hamilton Basin, a major rift-related depression bound by the Waipa Fault Zone.

[3] The largest debris avalanche (the Oparau breccia) cascaded at least 25 km southwest from Pirongia into the Kawhia Harbour and was larger in volume (3.3 km3) than the Mt.

The mountain contains unusually crystal-rich lavas of (ankaramite basalt) that also occur on Karioi, Kakepuku and Te Kawa but are not found elsewhere in New Zealand.

[1] Mount Pirongia is a popular place for hunters from Hamilton seeking a quick day trip hunt, holding several feral goat herds on its bush-clad slopes.

The subcanopy has tree ferns, including wheki and ponga, and nikau palm, with pigeonwood (porokaiwhiri), hīnau, pukatea, supplejack (kareao), māhoe, hangehange, kanono and toropapa.

Rātā replaces kohekohe at higher levels, until a change to upland forest (dominated by kāmahi, tawheowheo and tāwari) at about 650 m (2,130 ft).

Above 800 m (2,600 ft) there are also scattered Hall's totara, miro, rātā and horopito, and, near the summit, pāhautea (at its northern limit on the west coast), but no rimu.

[17] All the tracks are well signposted, with bright orange plastic waymarks[18] and near the summit have recently been laid with boardwalks (see photo below), some of them as part of Te Araroa long distance trail.