Orthoclase as a Carlsbad Twin from Loket, Czech Republic

Characteristic Carlsbad twin of orthoclase from Loket (Elbogen) near Karlovy Vary in the Czech Republic. Measuring 7.2 cm, the specimen shows the typical intergrowth of two orthoclase crystals according to the Carlsbad twin law. An interesting collector’s specimen from one of the classic feldspar twin localities in Bohemia.

Orthoclase Carlsbad Twin from Loket

This mineral specimen comes from Loket (Elbogen) in the Sokolov District, Karlovy Vary Region, Czech Republic. The historic locality in western Bohemia is particularly well known for its Carlsbad twins of orthoclase. Such crystal intergrowths are classic examples of twinning in feldspars.

The orthoclase specimen shows the characteristic intergrowth of two crystal individuals according to the Carlsbad twin law. This twinning is recognizable from the external crystal shape and can be observed particularly well from different viewing angles.

What Is a Carlsbad Twin?

In a Carlsbad twin, two crystal individuals are intergrown according to a specific crystallographic relationship. Their crystal lattices therefore have a fixed, symmetrical orientation relative to one another. Consequently, this is not a random intergrowth of two crystals but a regular form of crystal twinning.

Carlsbad twinning is especially common among feldspars. Orthoclase belongs to the feldspar group and has the chemical formula KAlSi₃O₈. It crystallizes in the monoclinic crystal system and is an important rock-forming mineral in many igneous rocks.

The name Carlsbad twin refers to the region around Karlovy Vary (Carlsbad). In particular, the occurrences near Loket have long been documented in mineralogical literature. Therefore, specimens from this locality are interesting not only because of their crystal forms but also as examples from a historic European mineral locality.

Measuring 7.2 × 4.4 × 2 cm, this specimen is of considerable size. Its clearly recognizable twinning makes it an illustrative collector’s specimen for enthusiasts of classic localities and distinctive crystal forms.