An almandine-garnet growing as a porphyroblast in a quartzitic gneiss. Almandine, also known incorrectly as almandite, is a species of mineral belonging to the Garnet Group The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives Quartzite (from German Quarzit) not to be confused with the Mineral Quartz, is a hard Metamorphic rock which was originally Gneiss (ˈnaɪs is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from preexisting formations that were originally This particular garnet measures 3 cm. A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth Location: Paraíba, Brazil. Paraíba (paɾaˈiba is one of the states of Brazil, located in the northeastern part of the country on the Atlantic coast where lies the easternmost |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld

Purple pyrope porphyroblasts in a peridotite, coin of 1 euro for scale. This article is about the mineral For the bird sometimes placed in the monotypic genus Pyrope see Fire-eyed Diucon. A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. 1 Euro coins (€1 or 1€ are made of two Alloys the inner part of Cupronickel, the outer part of nickel Brass. The yellow-brown groundmass is weathered olivine. The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or Crystals are embedded Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg Location: Otrøy, Western Gneiss Region, Caledonides, Norway. Otrøy is the largest island of Midsund municipality Møre og Romsdal county Norway The Caledonian orogeny is a mountain building event recorded in the Mountains and Hills of northern Scotland, Ireland, England, Norway ( Norwegian: Norge ( Bokmål) or Noreg ( Nynorsk) officially the Kingdom of Norway, is a Constitutional

A porphyroblast is a large mineral crystal in a metamorphic rock which has grown within the finer grained groundmass as a result of static recrystallisation in the rock. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or Crystals are embedded Recrystallization is a process by which deformed grains are replaced by a new set of undeformed grains that nucleate and grow until the original grains have been entirely Therefore porphyroblasts are almost always nice euhedral crystals. Euhedral Crystals are those that are well-formed with sharp easily-recognized faces

The most common porphyroblasts in metapelites (metamorphosed mudstones and siltstones) are garnets and staurolites, which stand out in well foliated metapelites (such as schists) against the platy mica matrix. Pelite ( Greek Pelos, Clay is a descriptive name for a Clastic rock with a grain size of less than 1/16mm (originally sand or silt Examples include Mudstone (also called mudrock) is a fine grained Sedimentary rock whose original constituents were Clays or Muds Grain size is up Siltstone is a Sedimentary rock which has a composition intermediate in grain size between the coarser Sandstones and the finer Mudstones and The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives Staurolite is a red brown to black mostly opaque nesosilicate Mineral with a white streak Foliation is any penetrative planar fabric present in rocks. Foliation is common to rocks affected by regional metamorphic compression typical of orogenic The schists form a group of medium-grade Metamorphic rocks chiefly notable for the preponderance of lamellar Minerals such as Micas chlorite The word "mica" is thought to be derived from the Latin word la micare, "glitteren" in reference to the brilliant appearance of this mineral (especially

A similar type of crystal is a phenocryst, a large crystal in an igneous rock. A phenocryst is a relatively large and usually conspicuous Crystal distinctly larger than the grains of the rock groundmass of a Porphyritic Igneous Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Porphyroblasts are often confused with porphyroclasts, which can also be large outstanding crystals, but which are older than the matrix of the rock. A porphyroclast is a Clast or Mineral fragment in a Metamorphic rock, surrounded by a Groundmass of finer grained Crystals Porphyroclasts

A rock which has many porphyroblasts is described as having a porphyroblastic texture.

Porphyroblasts do not rotate.

As they grow, the foliation is preserved in their crystal structure, which is helpful for tracking changing deformation planes.

See also

• List of rock textures
• Rock microstructure