peperite

thumb|Peperite at Puy de Crouel in Auvergne, France thumb|Peperite from Cumbria, England. This example was formed during the [[Ordovician Period and it is of andesitic composition.]] A peperite is a type of volcaniclastic rock consisting of sedimentary rock that contains fragments of younger igneous material and is formed when magma comes into contact with wet sediments. The term was originally used to describe rocks from the Limagne region of France, from the similarity in appearance of the granules of dark basalt in the light-coloured limestone to black pepper. Typically the igneous fragments are glassy and show chilled-margins to the sedimentary matrix, distinguishing them from clasts with a sedimentary origin.

==Terminology== The term has been used to describe a wide variety of rocks that are interpreted to have formed by the interaction between magma and sediments. This usage has led to overlap with other terms such as hyaloclastite. In the 2002 edition of "Igneous Rocks" by Le Maître et al., the definition is given as "A local term for a tuff or breccia, formed by the intrusion of magma into wet sediments. Usually consists of glassy fragments of igneous rock and some sedimentary rock", while White (2000) defines peperite as "a genetic term applied to a rock formed essentially in situ by disintegration of magma intruding and mingling with unconsolidated or poorly consolidated, typically wet sediments. The term also refers to similar mixtures generated by the same processes operating at the contacts of lavas and other hot volcaniclastic deposits with such sediments".