Hemimorphite



Hemimorphite is a zinc silicate hydroxide hydrate mineral. There have been no modern analytical studies of local hemimorphite. The analysis of Clarke and Steiger (1900) is in superb agreement with the above formula for hemimorphite.
Hemimorphite was first described formally by Seymour (1868), but was surely known before then. Most early references, through the time of Palache's monograph (1935), utilized the now-obsolete name calamine; but Cook (1868) described it as electric calamine, and Ingalls (1895) called it hydrowillemite. Most subsequent studies have used the now-correct name. Hemimorphite comprises, in part, together with clays and trivial smithsonite, a mixture called vaneuxemite by Shepard (1876). The early work is summarized by Palache (1935) and Frondel (1972). Thermal dehydration studies were provided by Faust (1951) and Taylor (1962), and infrared spectra are on file in the Smithsonian Institution.
Local hemimorphite varies substantially in its appearance. Fine 1-10 mm, colorless crystals are known from both deposits and were illustrated by Pratt (1894). The bulk of the Sterling Hill material, however, occurs as secondary, subparallel to divergent aggregates of crystals, forming mammillary masses, slabs, and stalactitic and crested masses. These range in size from microscopic specimens to very large specimens weighing tens of kilograms. Chalky and fibrous aggregates are also known. The color of massive hemimorphite varies from colorless (apparent white in the aggregate) to white, very light yellow, very light green, and light blue; apparently-black crystals result from included oxide minerals. The luster is vitreous, and the density is 3.48 g/cm3. Much local hemimorphite is fluorescent in shortwave and longwave ultraviolet with a weak white color, which varies in intensity with zoning. Minor cabochon gems have been cut from blue concentrically-banded material.
Sterling Hill is the source for the vast preponderance of local hemimorphite, but there have been no recent studies of the major occurrence. The bulk of the material was found in the old Passaic and Noble Mines, the open pits. On many specimens the terminations of the hemimorphite crystals are serrated and closely-spaced. Collectively the crystals resemble aggregates of maggots; hence the old miner's name, maggot-ore. These specimens, abundantly preserved, are among the best hemimorphite specimens world-wide and are represented in most systematic collections. When cleaned, most are white, lustrous, and very attractive; others have depositional stains which are interesting in other ways. The occurrence was mined extensively in the 1870's, and hemimorphite was at that time a chief ore of zinc from Sterling Hill.
A description of the surface occurrence from Mr. O. J. Conley, superintendent of the Noble Mine in 1878, is given by Palache (1935; pages 22-23). An occurrence with altered sulfides was reported by Jenkins and Misiur (1994). Alterations of hemimorphite have not been studied in situ; Roy and Mumpton (1956) and Takahashi (1960) provided experimental data on the solubility and alteration of synthetic hemimorphite.
At Franklin, hemimorphite is a moderately uncommon mineral, occurring in seams and as coatings and crystals in vugs. Fine specimens are known, but are scarce, occurring as druses and in vugs. It is known from the weathered northern end of the west limb which was exposed in the Precambrian.
Not all local hemimorphite is associated with the principal zinc deposits. Palache (1935) noted minor amounts he considered to be derived from sphalerite in late-stage sulfide veins. Hemimorphite was also reported and well-illustrated from the Buckwheat Dolomite by Peters et al. (1983). (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1853
     
 Formula: Zn4Si2O7(OH)2 · H2O
 Essential Elements: Hydrogen, Oxygen, Silicon, Zinc
 All Elements in Formula: Hydrogen, Oxygen, Silicon, Zinc
     
 IMA Status: Approved
     
Fluorescent Mineral Properties

 Shortwave UV light: Moderately bright to weak white and pale yellow, less common green, orange-yellow, blue
 Mid wave UV light: Moderately bright to weak white and pale yellow, less common green, orange-yellow, blue
 Longwave UV light: Moderately bright to weak white and pale yellow, less common green, orange-yellow, blue
 Additional Information: Phosphoresces moderately bright to weak white and pale yellow
     
 To find out more about this mineral at minDat's website, follow this link   Hemimorphite

     
 References:
Dunn, Pete J. (1995). Franklin and Sterling Hill New Jersey: the world's most magnificent mineral deposits. Franklin, NJ.: The Franklin-Ogdensburg Mineralogical Society. p.412

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.60


The Picking Table References
 PT Issue and PageDescription / Comment
V. 57, No. 2 - Fall 2016, pg. 20Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Hemimorphite
View IssueV. 35, No. 2 - Fall 1994, pg. 21A Complex Base-Metal Assemblage From the Sterling Mine New Jersey - Hemimorphite
View IssueV. 33, No. 2 - Fall 1992, pg. 10The Check List of Franklin-Sterling Hill Fluorescent Minerals - Hemimorphite (Fluorescent Info)
View IssueV. 24 No. 2 - Fall 1983, pg. 14Minerals of the Buckwheat Dolomite Franklin, New Jersey, Hemimorphite (small description)
View IssueV. 18, No. 2 - September 1977, pg. 14The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Hemimorphite
View IssueV. 7, No. 2 - August 1966, pg. 10The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Hemimorphite
     
Images

     
Hemimorphite, non-fluorescent from Sterling Hill Mine, NJ.
Hemimorphite, non-fluorescent from Sterling Hill Mine, NJ. From the collection of, and photo by Robert A. Boymistruk.


Maggot-ore hemimorphite from Sterling Hill Mine, NJ
Maggot-ore hemimorphite from Sterling Hill Mine, NJ. 3 5/8" x 2. From the collection of, and photo by Robert A. Boymistruk.


Botryoidal habit hemimorphite from Passaic pit, Sterling Hill Mine, NJ
Botryoidal habit hemimorphite from Passaic pit, Sterling Hill Mine, NJ. 3 1/2" × 3 1/4". From the collection of and photo by Ken Reynolds.







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