MINERALS INDEX

Actinolite

Albite

Allactite

Allanite

Amphibole Group

Andradite

Anglesite

Anhydrite

Anorthite

Apatite

ApatiteGroup

Apophyllite

Aragonite

Arsenates

Arsenides

Arseniosiderite

Arsenopyrite

Aurichalcite

Axinite

Azurite

Barite

Barylite

Barysilite

Bementite

Biotite

Borates

Bornite

Boroarsenates

Bustamite

Cahnite

Calamine

Calcite

Calcium larsenite

Carbonates

Celestite

Cerusite

Chalcocite

Chalcophanite

Chalcopyrite

Chloanthite

Chlorite

Chlorophoenicite

Chondrodite

Chysolite Group

Clinohedrite

Copper

Corundum

Corundum Group

Crocidolite

Cummingtonite

Cuprite

Cuspidine

Cyprine

Datolite

Desaulesite

Descloizite

Diopside

Dolomite

Edenite

Epidote

EpidoteGroup

FeldsparGroup

Ferroaxinite

Ferroschallerite

Fluoborite

Fluorite

Franklinite

Friedelite

Friedelite Group

Gageite

Gahnite

Galena

Ganophyllite

Garnet

Glaucochroite

Goethite

Graphite

Greenockite

Gypsum

Halloysite

Haloids

Hancockite

Hardystonite

Hastingsite

Hedyphane

Hematite

Hetaerolite

Heulandite

Hodgkinsonite

Holdenite

Humite Group

Hyalophane

Hydrohetaerolite

Hydrozincite

Ilmenite

Jeffersonite

Kentrolite

Larsenite

Lead

Leucaugite

Leucophoenicite

Limonite

Lollingite

Loseyite

Magnesium- chlorophoenicite

Magnetite

Malachite

Manganbrucite

Manganite

Manganosite

Marcasite

Margarosanite

Mcgovernite

Mica Group

Microcline

Millerite

Molybdenite

Mooreite

Muscovite

Nasonite

Native Elements

Neotocite

Niccolite

Norbergite

Oxides

Pargasite

Pectolite

Phlogopite

Phosphates, Arsenates and Vanadates

Prehnite

Psilomelane

Pyrite

Pyrochroite

Pyroxene Group

Pyrrhotite

Quartz

Rhodochrosite

Rhodonite

Roeblingite

Roepperite

Rutile

Scapolite

Schallerite

Schefferite

Serpentine

Serpentine Group

Siderite

Silicates

Silver

Smithsonite

Sphalerite

Spinel

Spinel Group

Stilbite

Sulphates

Sulphides and Arsenides

Sussexite

Svabite

Talc

Tennantite

Tephroite

Thomsonite

Thorite

Titanite

Tourmaline

Tremolite and Actinolite

Unconfirmed Species

Vanadates

Vesuvianite

Willemite

Xonotlite

Zeolites

Zinc schefferite

Zincite

Zircon

Zoisite

 

Hardystonite

Ca2ZnSi2O7
Tetragonal

Physical properties
Hardystonite is found in granular masses and in isolated grains in limestone, and crystals are not known. The cleavage is good parallel to the base and poor parallel to both prisms, and cleavage fragments may thus have a prismatic or even a cubic appearance. The hardness is 3 to 4, and the specific gravity is 3.39. The mineral is white to faintly pinkish, semitransparent, and has a vitreous luster. Under the iron-are spark gap it fluoresces a dull, faint violet or not at all. It is optically negative; the refractive indices are, for sodium light, w =1.6691 and e = 1.6568; for lithium light, w = 1.6758 and e = 1.6647, both 0.0002.

Composition
Hardystonite is a calcium zinc silicate allied to the tetragonal lead silicate ganomalite. It may contain small amounts of magnesium and manganese in place of part of the calcium and zinc, respectively.

Analyses of hardystonite
 

1

2

3

4

SiO2

38.10

37.78

36.59

38.30

Al2O3  

0.91

0.77

 
Fe2O3

0.57

0.43

   
FeO    

0.42

 
ZnO

24.30

25.38

22.47

25.94

MnO

1.50

1.26

1.23

 
CaO

33.85

34.22

35.16

35.76

MgO

1.62

0.26

1.47

 
K2O  

0.78

   
Na2O  

1.10

   
PbO    

1.99 a

 
Ignition

0.52

0.34

   
 

100.46

100.46

100.00

100.00

a Jenkins and Bauer state: "we have found from 0.66 to 3.55 percent of lead oxide in all the hardystonite analyzed."
1. Grains separated from massive granular ore by heavy solution. J. E. Wolff (185), analyst.
2. Coarse columnar masses. J. E. Wolff (185), analyst. (Minute inclusions seen in thin section may account for the large amount of alkalis found.)
3. Hardystonite, specific gravity 3.443. Jenkins and Bauer (243), analysts.
4. Composition computed from the formula.

The ratios, shown in the analyses, of ZnO to CaO to SiO2, are close to 2 : 1 : 2, leading to the formula Ca2ZnSi2O7. The lead is probably present in a calcium larsenite molecule.

Occurrence
Hardystonite was discovered and described by Wolff (185), and little has been added to his observations. It was first found in the Parker shaft at a depth of about 900 feet, in granular mixture with willemite, rhodonite, and franklinite. Later it was found in considerable abundance in several parts of the ore bodies worked through the Parker shaft, but it has not yet been identified from any other part of the deposit at Franklin. Masses of several pounds weight and of coarse columnar texture, free from any other mineral, have been found. It has also been seen associated with brown vesuvianite, with complex crystals of brown apatite, and intimately intermixed with franklinite and bright-green. willemite. It appears to have been formed under the influence, of the pneumatolytic conditions prevalent somewhere in that part of the mine, which developed such a, peculiar assemblage of minerals as is scarcely known elsewhere.

The presence of lead, shown by Jenkins and Bauer to exist in all hardystonite, is of economic importance, as it is injurious to the quality of the zinc produced from the ore. Hence the presence of all minerals contain lead is carefully checked in the assay office at the mines.

The composition of hardystonite is closely analog to that of melilite, and X-ray examination shows that the unit cell, space group, and atomic arrangement the same in the two minerals, which differ only in that hardystonite contains zinc in the place of magnesium-aluminum.

 


 
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This page created: January 12, 2001 6:22 PM