Willemite



Willemite is a zinc silicate mineral (Zn2SiO4) and an ore of zinc. It occurs commonly in granular aggregates with franklinite and zincite, often in a calcite matrix. Willemite also occurs in masses, hydrothermal veins and surface coatings, and several crystal habits, such as hexagonal crystals or acicular needles.  Specimens of fibrous willemite arranged in radial sprays are especially sought-after. Almost all willemite from Franklin, New Jersey and Sterling Hill in Ogdensburg, N.J. exhibits a bright green fluorescence under shortwave UV light, while the texture, habit, and especially the color seen in daylight can be quite varied. Willemite can appear red, brown, tan, pink, black, white, gray, blue, yellow, orange, or many shades of green in daylight. Fluorescent-mineral collectors have coined some nicknames to describe willemite colors, such as "seafoam," or “apple green.”

Willemite can form during exsolution, intimately mixed with other minerals; at Franklin these include pale green petedunnite, blue vesuvianite (var. cyprine), gray tephroite, or pink bustamite. At Sterling Hill the tephroite is usually brown, and can include striking patterns of willemite exsolution lamellae.

Some generalizations about willemite are useful. At Sterling Hill willemite is generally some shade of tan, brown or red. This variety had historically been called “troostite.” Sterling Hill also featured a “black ore” zone with willemite that appears black. At Franklin, green willemite is predominant, often found in gneissic layers with franklinite and zincite. It is sometimes found as massive green to brown or yellow, glassy material known as “gem” willemite, and has been cut into faceted gemstones.


 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1830
     
 Formula: Zn2SiO4
 Essential Elements: Oxygen, Silicon, Zinc
 All Elements in Formula: Oxygen, Silicon, Zinc
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
Fluorescent Mineral Properties

 Shortwave UV light: Bright to very bright yellowish-green, rarely moderately bright pale yellow to orange-yellow, very rarely pale blue
 Mid wave UV light: Bright to very bright yellowish-green
 Longwave UV light: Bright to very bright yellowish-green
 Additional Information: Occasional vivid, long-lasting green phosphorescence, rarely moderately bright pale yellow to orange-yellow
     
 To find out more about this mineral at minDat's website, follow this link   Willemite

     
 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.384

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.82


The Picking Table References
 PT Issue and PageDescription / Comment
V. 58, No. 1 - Spring 2017, pg. 20Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Willemite
V. 53, No. 1 - Spring 2012, pg. 36Exsolution Willemite: The Big Squeeze
V. 51, No. 2 - Fall 2010, pg. 19Unaltered Sterling Hill Willemite
View IssueV. 45, No. 1 - Spring 2004, pg. 14The Art of Fluorescent Mineral Photography, With Special Attention to the Minerals of Franklin and Sterling Hill Photographing the More Popular Franklin and Sterling Hill Fluorescent Minerals - Willemite
View IssueV. 36, No. 1 - Spring 1995, pg. 10Closest-Packing and Hydrogen Bonds in Minerals of the Franklin Marble, Paul B. Moore - Willemite
View IssueV. 33, No. 2 - Fall 1992, pg. 11The Check List of Franklin-Sterling Hill Fluorescent Minerals - Willemite (Fluorescent Info)
View IssueV. 18, No. 2 - September 1977, pg. 20The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Willemite
View IssueV. 13, No. 2 - August 1972, pg. 13The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Willemite (Fluorescent Info)
View IssueV. 10, No. 1 - February 1969, pg. 9Harvard Research on Franklin Minerals - Willemite
View IssueV. 8, No. 2 - August 1967, pg. 6Mineralogical Data - Willemite
View IssueV. 7, No. 2 - August 1966, pg. 14The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Willemite
View IssueV. 5, No. 2 - August 1964, pg. 12Willemite (small article)
View IssueV. 4, No. 2 - August 1963, pg. 8Willemite and Its Polymorphs
     
Willemite Images, for more go to our White Light Willemite Page

     
Black willemite, Sterling Hill Mine "cross-member"Black willemite, Sterling Hill Mine "cross-member" under shortwave UV Light
Black willemite from the Sterling Hill mine "cross-member," a body of ore between the East and West veins. Photo by JVF.
Black willemite from the Sterling Hill mine "cross-member," a body of ore between the East and West veins under shortwave UV light. The willemite fluoresces green. Photo by JVF.


"Brick red" willemite, calcite, franklinite, Sterling Hill Mine"Brick red" willemite, calcite, franklinite, Sterling Hill Mine under shortwave UV Light
"Brick red" willemite with calcite (white) and franklinite (black), from the Sterling Hill Mine. Photo by JVF.
"Brick red" willemite with calcite and franklinite, from the Sterling Hill Mine under shortwave UV light. The willemite fluoresces green and the calcite red, franklinite is non-fluorescent. Photo by JVF.


Red willemite, calcite and franklinite, Sterling Hill MineRed willemite, calcite and franklinite, Sterling Hill Mine under shortwave UV Light
Red willemite with calcite (white) and franklinite (black), from the Sterling Hill Mine. Photo by JVF.
Red willemite with calcite and franklinite, from the Sterling Hill Mine under shortwave UV light. The willemite fluoresces green and this calcite is non-fluorescent. Photo by JVF.


Grape willemite with calcite and magnetite from Franklin NJGrape willemite with calcite and magnetite from Franklin NJ under shortwave UV Light
Grape willemite with calcite (white) and magnetite (black) from the Franklin Mine, Franklin, NJ. Photo by WP.
Grape willemite with calcite (white) and magnetite (black) from the Franklin Mine, Franklin, NJ under shortwave UV light. The grape willemite fluoresces green and the calcite red, magnetite is non-fluorescent. Photo by WP.


Pink willemite with calcite and franklinite, from the Sterling Hill Mine NJ.Pink willemite with calcite and franklinite, from the Sterling Hill Mine NJ. under longwave UV Light
Pink willemite with calcite (white) and franklinite (black), from the Sterling Hill Mine, NJ. Photo by WP.
Pink willemite with calcite and franklinite, from the Sterling Hill Mine, NJ under longwave UV light. The willemite fluoresces green and the calcite pale red, franklinite is non-fluorescent. Photo by WP.
Pink willemite with calcite and franklinite, from the Sterling Hill Mine NJ. under shortwave UV Light
Pink willemite with calcite and franklinite, from the Sterling Hill Mine, NJ under shortwave UV light. The willemite fluoresces green and the calcite red, franklinite is non-fluorescent. Photo by WP.


Green willemite, glaucochroite and franklinite, from Franklin, NJ.Green willemite, glaucochroite and franklinite, from Franklin, NJ. under longwave UV Light
Green willemite, glaucochroite (gray) and franklinite (black), from Franklin, NJ. Photo by WP.
Green willemite, glaucochroite and franklinite, from Franklin, NJ under longwave UV light. The willemite fluoresces green and the glaucochroite and franklinite is non-fluorescent. Photo by WP.
Green willemite, glaucochroite and franklinite, from Franklin, NJ. under midwave UV LightGreen willemite, glaucochroite and franklinite, from Franklin, NJ. under shortwave UV Light
Green willemite, glaucochroite and franklinite, from Franklin, NJ under mid-wave UV light. The willemite fluoresces green and the glaucochroite and franklinite is non-fluorescent. Photo by WP.
Green willemite, glaucochroite and franklinite, from Franklin, NJ under shortwave UV light. The willemite fluoresces green and the glaucochroite and franklinite is non-fluorescent. Photo by WP.


Yellow willemite, calcite and franklinite, from Franklin, NJ.Yellow willemite, calcite and franklinite, from Franklin, NJ. under longwave UV Light
Yellow willemite, calcite (white) and franklinite (black), from Franklin, NJ. Photo by WP.
Yellow willemite, calcite and franklinite, from Franklin, NJ under longwave UV light. The willemite fluoresces green and the calcite and franklinite is non-fluorescent. Photo by WP.
Yellow willemite, calcite and franklinite, from Franklin, NJ. under shortwave UV Light
Yellow willemite, calcite and franklinite, from Franklin, NJ under shortwave UV light. The willemite fluoresces green and the calcite red-orange, franklinite is non-fluorescent. Photo by WP.


Willemite crystals on willemite / franklinite matrix from Franklin, NJ.Willemite crystals on willemite / franklinite matrix from Franklin, NJ. under longwave UV Light
Willemite crystals on willemite / franklinite matrix from Franklin, NJ. Photo by WP.
Willemite crystals on willemite / franklinite matrix from Franklin, NJ under longwave UV light. The willemite fluoresces green and the franklinite is non-fluorescent. Photo by WP.
Willemite crystals on willemite / franklinite matrix from Franklin, NJ. under shortwave UV Light
Willemite crystals on willemite / franklinite matrix from Franklin, NJ under shortwave UV light. The willemite fluoresces green and the franklinite is non-fluorescent. Photo by WP.


Gemmy root beer and green willemite, minor franklinite from Franklin, NJ.Gemmy root beer and green willemite, minor franklinite from Franklin, NJ. under longwave UV Light
Gemmy root beer and green willemite, minor franklinite from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.
Gemmy root beer and green willemite, minor franklinite from Franklin, NJ under longwave UV light. The willemite fluoresces green and the franklinite is non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.
Gemmy root beer and green willemite, minor franklinite from Franklin, NJ. under shortwave UV Light
Gemmy root beer and green willemite, minor franklinite from Franklin, NJ under shortwave UV light. The willemite fluoresces green and the franklinite is non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


Radiating willemite on dolomite with garnet and minor franklinite from Franklin, NJ.Radiating willemite on dolomite with garnet and minor franklinite from Franklin, NJ. under longwave UV Light
Radiating willemite (white) on dolomite (gray) with garnet (brown) and minor franklinite (black) from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.
Radiating willemite on dolomite with garnet and minor franklinite from Franklin, NJ under longwave UV light. The willemite fluoresces green and the dolomite, garnet and franklinite are non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.
Radiating willemite on dolomite with garnet and minor franklinite from Franklin, NJ. under shortwave UV Light
Radiating willemite on dolomite with garnet and minor franklinite from Franklin, NJ under shortwave UV light. The willemite fluoresces green and the dolomite, garnet and franklinite are non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


Red willemite, green andradite garnet and franklinite from Franklin, NJRed willemite, green andradite garnet and franklinite from Franklin, NJ under longwave UV Light
Willemite (gemmy red and white), andradite garnet (greenish brown) and franklinite (black) from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.
Willemite, andradite garnet and franklinite from Franklin, NJ under longwave UV light. The willemite fluoresces green, the garnet and franklinite are non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.
Red willemite, green andradite garnet and franklinite from Franklin, NJ under shortwave UV Light
Willemite, andradite garnet and franklinite from Franklin, NJ under shortwave UV light. The willemite fluoresces green, the garnet and franklinite are non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


Brown tephroite with exsolution willemite lamellae, minor franklinite and calcite from Sterling Hill Mine, NJBrown tephroite with exsolution willemite lamellae, minor franklinite and calcite from Sterling Hill Mine, NJ under shortwave UV Light
Brown tephroite with exsolution willemite lamellae, minor franklinite (black) and calcite (white) from Sterling Hill Mine, NJ. 4 1/4" x 3". Photo by WP.
Brown tephroite with exsolution willemite lamellae, minor franklinite and calcite from Sterling Hill Mine, NJ under shortwave UV light. The willemite fluoresces green, calcite orange-red, the tephroite and franklinite are non-fluorescent. 4 1/4" x 3". Photo by WP.


Mylonitized ore, willemite, franklinite and calcite from Sterling Hill, Ogdensburg, NJMylonitized ore, willemite, franklinite and calcite from Sterling Hill, Ogdensburg, NJ under shortwave UV Light
Mylonitized ore, willemite (brown), franklinite (black) and calcite (white) from the 750 foot level near the zero fault, Sterling Hill, Ogdensburg, NJ. 5 1/2" x 3 1/2". From the collection of Zack and Ralph Bonard, photo by WP.
Mylonitized ore, willemite, franklinite and calcite from the 750 foot level near the zero fault, Sterling Hill, Ogdensburg, NJ under shortwave UV light. The willemite fluoresces green, calcite red-orange, and the franklinite is non-fluorescent. 5 1/2" x 3 1/2". From the collection of Zack and Ralph Bonard, photo by WP.




For more willemite images, go to our White Light Willemite Page


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