Hendricksite

Hendricksite
Hendricksite
General
Category	Mineral
Formula; (repeating unit)	KZn3(Si3Al)O10(OH)2
IMA symbol	Hds
Strunz classification	09.EC.20
Dana classification	71.2.2b.6
Crystal system	Monoclinic
Crystal class	Prismatic (2/m)
Space group	B2/m
Unit cell	499.58 Å³
Identification
Formula mass	493.25
Color	Copper-, bronze brown, dark reddish brown to reddish black
Cleavage	Perfect on {001}
Mohs scale hardness	2.5 - 3
Diaphaneity	Translucent
Specific gravity	2.86 - 3.43
Optical properties	Biaxial (-)
Refractive index	nα = 1.598 - 1.624 nβ = 1.658 - 1.686 nγ = 1.660 - 1.697
Birefringence	0.062 - 0.073
Pleochroism	X = pale yellow, Y = light chestnut brown, Z = light chestnut brown
2V angle	Measured 2°- 8°, calculated 20°- 44°
Dispersion	Slight, r < v
Common impurities	Ti, Fe, Ca, Ba, Li, Na, F

Hendricksite is a member of the trioctahedral micas group. The mineral was named by Clifford Frondel and Jun Ito in honor of Sterling Brown Hendricks, who studied micas. Zinc in the formula can be replaced with manganese(II) or magnesium. Currently, this is the only mica known for its zinc dominancy.^[2] It was approved in 1966 by the IMA. It has a barely detectable, 1% radioactivity measured by GRapi (Gamma Ray American Petroleum Institute Units). It mostly consists of oxygen (38.92%), zinc (18.56%), silicon (15.37%) and manganese (10.02%), but otherwise contains potassium (7.13%) which gives the gem its irradiative attributes, aluminium (7.11%), magnesium (2.46%) and hydrogen (0.41%). It has pleochroic attributes, which is an optical phenomenon that makes gems to be seen a different color depending on the axis it is seen. 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.^[3]

References[]

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85: 291–320.
^ "Hendricksite". www.mindat.org. Retrieved 2021-02-11.
^ "Hendricksite Mineral Data". webmineral.com. Retrieved 2021-02-11.

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[1] Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85: 291–320.

[2] "Hendricksite". www.mindat.org. Retrieved 2021-02-11.

[3] "Hendricksite Mineral Data". webmineral.com. Retrieved 2021-02-11.

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