Jerrygibbsite is a rare

silicate mineral Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

with the chemical formula . Jerrygibbsite was originally discovered by Pete J. Dunn in 1984, who named it after mineralogist Gerald V. Gibbs (born 1929). It has only been reported from the type locality of

Franklin Furnace Franklin Furnace, also known as the Franklin Mine, is a famous mineral location for rare zinc, iron, manganese minerals in old mines in Franklin, New Jersey, United States. This locale produced more species of minerals (over 300) and more differ ...

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delawa ...

, United States, and in

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

's Otjozondjupa region. Jerrygibbsite is member of the leucophoenite family of the

humite group Humite is a mineral found in the volcanically ejected masses of Vesuvius Mount Vesuvius ( ; it, Vesuvio ; nap, 'O Vesuvio , also or ; la, Vesuvius , also , or ) is a somma-stratovolcano located on the Gulf of Naples in Campania, Ital ...

. It is always found with these two minerals. It is a dimorph of sonolite.

Discovery

The mineral jerrygibbsite was discovered in 1984 by Pete Dunn while conducting an X-ray spectrographic analysis of a sample previously assumed to be leucophoenicite. All samples found of jerrygibbsite are impure. All are incorporated within leucophoenicite, many by mixed layering, and tend to be found with many

manganese Manganese is a chemical element with the Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of ...

humites such as sonolite. Physical properties are similar to those of leucophoenicite and sonolite, including hardness, coloring, and density.

Composition

The formula for jerrygibbsite is (, although it often contains impurities of

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

.Webmineral- Jerrygibbsite
Referenced November 4, 2007 The idealized formula is Mn₉(SiO₄)₄(OH)₂ which is the same ideal formula as sonolite, a member of the humite group.Dunn, Pete J. (1984). "Jerrygibbsite, a new polymorph of (Mn,Zn)9(SiO4)4(OH)2 from Franklin, New Jersey, with new data on leucophoenicite".

American Mineralogist ''American Mineralogist: An International Journal of Earth and Planetary Materials'' is a peer-reviewed scientific journal covering the general fields of mineralogy, crystallography, geochemistry, and petrology. It is an official journal of the Min ...

69: 546–552. Jerrygibbsite has been found to be dimorphous with sonolite.

Geologic occurrence

Jerrygibbsite has been found only in the

mine in Franklin, New Jersey, and in the Kombat Mines in

. Most of the minerals in the humite group have been found only here, as well as leucophoenicite. Jerrygibbsite has been found to occur in contact with

willemite Willemite is a zinc silicate mineral () and a minor ore of zinc. It is highly fluorescent (green) under shortwave ultraviolet light. It occurs in a variety of colors in daylight, in fibrous masses and apple-green gemmy masses. Troostite is a v ...

, zincite, and sonolite in an uncommon assemblage. Jerrygibbsite typically occurs as a massive mineral in interlocking anhedral crystals, up to 0.5 mm × 2.0 mm, which display a typical metamorphic texture. Subsequent finds from the Namibia mines were of two different textures.

Physical properties

Jerrygibbsite, in pure form, is a violet-pink mineral with a light pink streak. It has a calculated density of 4.045 g/cm³, and a tested density of 4.00 g/cm³, agreeing favorably, since measurements used to test density have few significant figures. It has a hardness of about 5.5, that of a knife blade. The general luster is vitreous, or shiny. Crystals are generally transparent to translucent. Crystals are not

luminescent Luminescence is spontaneous emission of light by a substance not resulting from heat; or "cold light". It is thus a form of cold-body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions or stress on a crystal ...

fluorescent Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, ...

. Jerrygibbsite forms orthorhombic crystals with an imperfect cleavage along the {001} plane, which can be seen by opaque lamellae alternating with the transparent jerrygibbsite. Optically, jerrygibbsite is negative biaxial with 2''V'' = 72˚ and a maximum

birefringence Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefri ...

of 0.017. In

thin section In optical mineralogy and petrography, a thin section (or petrographic thin section) is a thin slice of a rock or mineral sample, prepared in a laboratory, for use with a polarizing petrographic microscope, electron microscope and electron ...

, jerrygibbsite appears light pink. The crystal structure described by Kato is the equivalent of a unit-cell-twinned sonolite in which the cells are related by a ''b''/4 glide plane.

References

Humite group Nesosilicates Manganese(II) minerals Orthorhombic minerals Minerals in space group 33

Discovery

Composition

Geologic occurrence

Physical properties

See also

References