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.

For more information on willemite, follow this link (willemite) to an excerpt from Pete Dunn’s manuscript, Franklin and Sterling Hill, New Jersey: the world’s most magnificent mineral deposits.

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

Willemite Images, for more go to our White Light Willemite Page


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 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 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 (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 (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. The willemite fluoresces green and the calcite red, franklinite is non-fluorescent. Photo by WP.


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 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 (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. 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. 2 3/4" x 1 3/4". 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. 2 3/4" x 1 3/4". Photo by WP.

Willemite crystals on willemite / franklinite matrix from Franklin, NJ under shortwave UV light. The willemite fluoresces green and the franklinite is non-fluorescent. 2 3/4" x 1 3/4". Photo by WP.


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. The willemite fluoresces green and the franklinite is non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


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. The willemite fluoresces green and the dolomite, garnet and franklinite are non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


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.

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 (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 (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.


Gemmy willemite crystals (yellow-green) from Franklin, NJ. 2 1/4" x 2 1/4". From the collection of, and photo by Robert A. Boymistruk.		Gemmy willemite crystals from Franklin, NJ under shortwave UV light. The willemite fluoresces green. 2 1/4" x 2 1/4". From the collection of, and photo by Robert A. Boymistruk.


Clear willemite crystal, willemite (glassy gray) and friedelite crystals (tan) from the Sterling Hill Mine, Ogdensburg, NJ. Field of view 9/16". From the collection of, and photo by Robert A. Boymistruk.		Clear willemite crystal, willemite and friedelite crystals from the Sterling Hill Mine, Ogdensburg, NJ under shortwave UV light. The willemite fluoresces green. Field of view 9/16". From the collection of, and photo by Robert A. Boymistruk.


Beta-willemite (tan), franklinite (black) and calcite (white) from the Sterling Hill Mine, Ogdensburg, NJ. 4" x 3". From the collection of Zack and Ralph Bonard, photo by Ralph Bonard.		Beta-willemite, franklinite and calcite from the Sterling Hill Mine, Ogdensburg, NJ under shortwave UV light. The beta-willemite fluoresces yellow. 4" x 3". From the collection of Zack and Ralph Bonard, photo by Ralph Bonard.