Paleogene
It is a part of the Cenozoice Era which comprises of the Paleocene, Eocene and Oligocene epochs. It extends from 65.5. to 23.8 million years ago.

Paleontology
It is the science and study of previous life forms, mainly in the form of fossils.

Paleontologist
One who practice the subject of paleontology.

Paleozoic Era
It is a period of geological time which extends from 545 to 245 million years ago. It is subdivided into the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian Periods.

Paragenesis
It is the term used for the crystallization mode of one mineral in retrospect to other.

Pearly (luster)
It is term used for that type of luster which is similar to the inner part of a mollusk shell or shirt button. Many forms of mica exhibit such luster. Some minerals having this luster may also have an iridescent hue. Few minerals even exhibit a pearly luster on cleavage cracks which is parallel and below the reflecting surface of a mineral.

Pegmatite
It is a very coarse-grained igneous rock which is characterized by crystals of more than 3 cm in length.

Penetration
It is the formation of a crystal penetration through a rock or that of another crystal.

Peridotite
It is a class of ultramafic rocks which consists of predominantly olivine. It may be with or without other ferromagnesian (Fe-Mg) minerals.

Permian
It is a period of geological time which extends from 280 to 255 million years ago. It marks the end of the Paleozoic Era.

Petrology
It is a type of geology which deals with the formation, composition, and source of rocks.

Petrologist
One who practice in the subject of petrology.

pH
It is a measurement of acid or alkaline present in a material. The scale of measurement is 0 - 14. 7 is neutra, below it is acid and above, alkaline. pH stands for "potential of Hydrogen." It is names such because hydrogen causes a material to be acidic.

Phosphates
It is group of minerals being compounds of one or more metallic elements associated with the phosphate radical (PO₄). Phosphates are classified together with arsenates as well as vanadates. Most of the phosphates are heavy, but none of them are hard. They are generally brittle and occurs in small crystals or compact aggregates.

Pliocene
It is a period of geological time which extends from 5.3 to 1.81 million years ago.

Porous
It is a term used for those minerals which contain rounded, tiny holes throughout. Many of them can be dyed.

Precambrian
It is the extensive period of geological time which is literally used as "before the Cambrian." It contains around 90% of all geological time and it ends approximately 545 million years ago.

Proterozoic
It is a period of geological time which is the uppermost of the two main Precambrian divisions. It extends from 2500 to 545 million years ago.

Pure
Free of impurities.

Pyncnometer
It is an instrument which measures specific gravity.

Pyramidal
One which is shaped like a pyramid, having a pointed top.