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|System:||Tetragonal||Colour:||light brownish white, ...|
|Hardness:||3 - 4|
|Name:||Named in 1899 by John E. Wolff after Hardyston Township, Sussex County, New Jersey, USA, locality of the Franklin orebody prior to incorporation of Franklin Borough in 1913. Hardyston Township surrounds the borough of Franklin today.|
In daylight, natural hardystonite is a very non-descript massive ashen white mineral distinguished from massive calcite by a lack of cleavage and a somewhat greasy luster. (Note: Many photographers over-expose images of hardystonite to accentuate the blue fluorescent brightness. Such photos are often called "eBay blue", because deceptive sellers wish to increase their sales, but disappointed buyers feel cheated because the actual fluorescence of hardystonite is fairly dim compared with associated species such as calcite, willemite, or esperite.)
Visit gemdat.org for gemological information about Hardystonite. Currently in public beta-test.
Classification of Hardystonite
|IMA status:||Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"|
|Strunz 8th edition ID:||8/C.02-40|
|Nickel-Strunz 10th (pending) edition ID:||9.BB.10|
9 : SILICATES (Germanates)
B : Sorosilicates
B : Si2O7 groups, without non-tetrahedral anions; cations in tetrahedral  and greater coordination
|Dana 8th edition ID:||184.108.40.206|
55 : SOROSILICATES Si2O7 Groups,Generally with no Additional Anions
4 : Si2O7 Groups, Generally with No Additional Anions with cations in  and lower coordination
|Hey's CIM Ref.:||14.7.14|
14 : Silicates not Containing Aluminum
7 : Silicates of Ba, Sr and Zn
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Type Occurrence of Hardystonite
|Type Locality:||Franklin Mine, Franklin, Franklin Mining District, Sussex Co., New Jersey, USA|
|Year of Discovery:||1899|
|Geological Setting of type material:||Occurs in a metamorphosed zinc-manganese-iron silicate-oxide orebody.|
Physical Properties of Hardystonite
|Lustre:||Adamantine, Resinous, Dull|
|Colour:||light brownish white, pale greyish-white, whitish, very pale pinkish|
|Hardness (Mohs):||3 - 4|
Crystallography of Hardystonite
|Class (H-M):||4 2m - Scalenohedral|
|Space Group:||P4 21m|
|Cell Parameters:||a = 7.8287(16) Å, c = 5.0140(2) Å|
|Ratio:||a:c = 1 : 0.64|
|Unit Cell Volume:||V 307.30 Å³ (Calculated from Unit Cell)|
|Morphology:||Large, rough crystals rare embedded in calcite or other matrix.|
|X-Ray Powder Diffraction:|
Radiation - Copper Kα
Data courtesy of RRUFF project at University of Arizona, used with permission.
Optical Data of Hardystonite
|RI values:||nω = 1.672 nε = 1.661|
|Maximum Birefringence:||δ = 0.011|
Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Chemical Properties of Hardystonite
|Simplified for copy/paste:||Ca2Zn(Si2O7)|
|Essential elements:||Ca, O, Si, Zn|
|All elements listed in formula:||Ca, O, Si, Zn|
|Analytical Data:||Often replaced by, or being replaced by esperite. The latter condition very apparent under UV light as whisps and veils of esperite invading the hardystonite.|
Relationship of Hardystonite to other Species
|Member of:||Melilite Group|
|Other Members of Group:|
|Related Minerals - Nickel-Strunz Grouping):|
|Related Minerals - Hey's Index Grouping:|
Other Names for Hardystonite
|Fluorescence in UV light:||Dull persistent purple to blue (SW UV); blue (LW UV).|
|Health Warning:||No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.|
References for Hardystonite
Palache, C. (1935), USGS PP 180: 94.
Dunn, Pete J. (1995): Pt3: 411-412.
Zeitschrift für Kristallographie: 130: 427-437.
Internet Links for Hardystonite
Localities for Hardystonite
The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
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Locality Updated: St Just District, Cornwall, England, UKFrom Peter Haas, 2nd Sep 2014 01:58:55