The Parâng Mountains consist predominantly of crystalline rocks, peripherally covered with patches of sediments from the Paleozoic, Mesozoic (massive limestone, conglomerates) and Cenozoic eras, mixed with large areas of granite outcrops.

On the southern slope, sedimentary rocks from the Mesozoic era can be found, more exactly massive limestone from the Jurassic period.

The newest rocks are found on the southern frame of the mountains and in the north-west, where it is bordered by the Petrosani Depression.

The nature of the rocks favored the emergence of bulk, rounded ridges, separated by deep valleys.

[1][2] The general layout of the main ridge on a west–east axis and its altitudes of over 2000m makes the Parâng mountains an orographic dam in the way of the air masses that flow on the north to north-west and south to south-west directions.

The second layer mostly extended on the northern and western slopes, between 1000m and 1750m, and is composed of norway spruce forests and, locally, european silver fir.

Among mammals, the grey wolf, fox, wild boar, brown bear, eurasian lynx and red deer can be found.