Hendricksite is a member of the trioctahedral

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...

s group. The mineral was named by Clifford Frondel and Jun Ito in honor of Sterling Brown Hendricks, who studied micas. It was approved in 1966 by the IMA.

Physical properties

Hendricksite can either form short prismatic crystals, or foliated ones that are platy and seem two dimensional. It occurs in clusters, and these aggregates have interlocking crystals. These crystals are more commonly anhedral - a crystal with no faces, but rarely they can be

euhedral Euhedral crystals (also known as idiomorphic or automorphic crystals) are those that are well-formed, with sharp, easily recognised faces. The opposite is anhedral (also known as ''xenomorphic'' or ''allotriomorphic''): a rock with an anhedral ...

- crystals with well defined surfaces. The anhedral crystals can grow up to 30 cm, and are commonly deformed, while the euhedral crystals can reach 14 cms in size of mechanical deformation. It has

pleochroic Pleochroism (from Greek πλέων, ''pléōn'', "more" and χρῶμα, ''khrôma'', "color") is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light. Backgroun ...

attributes, which is an optical phenomenon that makes minerals to be seen a different color depending on the axis it is inspected on. On the X axis, it can be seen in a pale brown color, while on the Y and Z axis it is seen in a light chestnut brown color. It doesn't show any fluorescence under either shortwave, or longwave

ultraviolet light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

Chemical properties

It mostly consists of oxygen (38.92%), zinc (18.56%), silicon (15.37%) and manganese (10.02%), but otherwise contains potassium (7.13%), aluminium (7.11%), magnesium (2.46%) and a negligible amount of hydrogen (0.41%). It has a barely detectable, 1% radioactivity measured by GRapi (Gamma Ray American Petroleum Institute Units) due to its potassium content, which gives the mineral its radioactive attributes. Zinc in hendricksite's formula can be replaced with manganese(II) or magnesium. Currently, this is the only mica known for its zinc dominancy, and it is the zinc analogue of

phlogopite Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica. Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg3AlSi3O ...

annite Annite is a phyllosilicate mineral in the mica family. It has a chemical formula of KFe32+AlSi3O10(OH)2. Annite is the iron end member of the biotite mica group, the iron rich analogue of magnesium rich phlogopite. Annite is monoclinic and cont ...

, and shirozulite. It can have calcium, iron, titanium, barium, lithium, natrium and fluorine impurities. It has three known

polytypes In materials science, polymorphism describes the existence of a solid material in more than one form or crystal structure. Polymorphism is a form of isomerism. Any crystalline material can exhibit the phenomenon. Allotropy refers to polymorphism ...

, which include 1M, 2M₁, and 3A. Hendricksite can be included in a solid solution series with zincohendricksite and manganoanhendricksite being the endmembers, a solid solution series meaning the three sharing a general formula but having a substitution of elements in at least one of the atomic sites. A part of the solid solutions series might be magnesium bearing hendricksite, the series perhaps being complete to

and partially to

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more alumino ...

. In the case of trioctahedral micas, the ellipsoids of the cationic sites have an uniaxial positive optical property, elongated to ''c''. However, in hendricksite's case this is only typical for the two zinc-free sides. In the octahedras containing zinc, the ellipsoids are uniaxial negative and flattened to ''a''.

Occurrences and localities

It can appear only in metamorphosed stratiform zinc deposits, in irregular lens or sheet like skarn bodies. It can be found in the Franklin mine in New Jersey, USA. The mineral can be found at the Sterling hill as well, although it is much rarer due to the higher iron and magnesium concentrations. It occurs with

vesuvianite Vesuvianite, also known as idocrase, is a green, brown, yellow, or blue silicate mineral. Vesuvianite occurs as tetragonal crystals in skarn deposits and limestones that have been subjected to contact metamorphism. It was first discovered within ...

bustamite Bustamite is a calcium manganese inosilicate (chain silicate) and a member of the wollastonite group. Magnesium, zinc and iron are common impurities substituting for manganese. Bustamite is the high-temperature polymorph of CaMnSi2O6 and johanns ...

and

feldspars Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...

, additional associated minerals being minerals of the

axinite Axinite is a brown to violet-brown, or reddish-brown bladed group of minerals composed of calcium aluminium boro-silicate, . Axinite is pyroelectric and piezoelectric. The axinite group includes: *Axinite-(Fe) or ferroaxinite, Ca2Fe2+Al2BOSi4O15( ...

group,

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

rhodonite Rhodonite is a manganese silicate minerals, inosilicate, (Mn, Fe, Mg, Ca)SiO3 and member of the pyroxenoid group of minerals, crystallizing in the triclinic system. It commonly occurs as cleavable to compact masses with a rose-red color (the name ...

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 vari ...

hancockite Epidote is a calcium aluminium iron sorosilicate mineral. Description Well developed crystals of epidote, Ca2Al2(Fe3+;Al)(SiO4)(Si2O7)O(OH), crystallizing in the monoclinic system, are of frequent occurrence: they are commonly prismatic in habi ...

, as well as andrasite.

References

{{Reflist Zinc minerals Mica group Phyllosilicates Minerals described in 1966