Frankamenite is the fluorine

Fluorine

Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...

-dominate variation of the rare mineral canasite with a general formula of K₃Na₃Ca₅(Si₁₂O₃₀)[F,(OH)]₄·(H₂O).

Frankamenite belongs to the triclinic crystal system

Crystal system

In crystallography, the terms crystal system, crystal family, and lattice system each refer to one of several classes of space groups, lattices, point groups, or crystals...

, with the bases of its structure containing Ca-Na mixed octahedra joined by octagonal tubes SiO₄ of the composition (Si₁₂O₃₀). Frankamenite has six Ca-Na mixed positions distributed amongst these octahedra, reflecting its varying compositions.

Frankamenite was named for the Russian mineralogist-crystallographer

Crystallographer

Crystallographer could refer to someone who practices:*X-ray crystallography*Crystallography...

 V. A. Frank-Kamentsky, who discovered the mineral.

Frankamenite occurs in association with the rare mineral charoite

Charoite

Charoite , pronounced CHAR-oh-ite, is a rare mineral, first described in 1978 and named for the Chara River. It has been reported only from the Sakha Republic, Yakutia, Siberia, Russia...

, which is found only in the Sakha Republic, Yakutia, Siberia

Siberia

Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

, Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

. Here, metasomatism

Metasomatism

Metasomatism is the chemical alteration of a rock by hydrothermal and other fluids.Metasomatism can occur via the action of hydrothermal fluids from an igneous or metamorphic source. In the igneous environment, metasomatism creates skarns, greisen, and may affect hornfels in the contact...

 enriches a syenite

Syenite

Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or...

 massif

Massif

In geology, a massif is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole...

 with potassium

Potassium

Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

 when it comes into contact with a limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 at around 200-250 °C. This metamorphic process

Metamorphism

Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...

 produces a potassium feldspar metasomatite, the typical geological environment for canasite and, therefore, frankamenite. Frankamenite and charoitein are exclusive to the Sakha Republic in this sort of environment, as mineralogists have yet to discover the minerals elsewhere.