AXINITE-(Mn)

Manganaxinite (Axinite-(Mn)) is a calcium manganese aluminum boron silicate hydroxide mineral of the axinite group. Franklin material varies in composition, but there is only limited solid-solution toward ferroaxinite or magnesioaxinite. Most Franklin specimens have MnO values of 12-16 wt. %.
Manganaxinite was described from Franklin by Genth et al. (1891) who provided the first morphological description and chemical analysis. Ford (1903) established the correct water content using Franklin samples similar to those described by Genth. The morphology of the superb yellow crystals was the subject of additional detailed studies by Aminoff (1919) and Palache (1935). Manganaxinite is the species generally referred to as common axinite in the older literature.
Franklin manganaxinite occurs in two substantially different habits: as massive, light-yellow to white material and as rich deep-yellow to light-yellow to colorless euhedral crystals up to 1 cm in size. The yellow crystals were the subject of all the early investigations. Franklin crystals are mostly yellow; brownish crystals have been found at Sterling Hill. Crystals are sharp and wedge-shaped and have typical axinite habits; excellent morphological descriptions are provided by Palache (1935). The cleavage is good; the density is 3.328 g/cm³; and the luster is vitreous.
The rich yellow, well-crystallized manganaxinites and the distinctly yellow massive material generally have no discernible fluorescence in ultraviolet. However, nearly-colorless euhedral crystals and some massive light-yellow to white samples fluoresce with a strong red color in shortwave and a less intense red in longwave ultraviolet. The intensity of the fluorescence varies. There is insufficient data to establish firm correlations between fluorescence and composition, but the samples which fluoresce have minimal FeO and MnO values less than 12 wt. %. Massive manganaxinite can be confused with a number of species, among them andradite, grossular, and fine-grained feldspars.
Manganaxinite is known from both Franklin and Sterling Hill. However, the overwhelming preponderance of material, and the best, is from Franklin, specifically from the Trotter and Parker Mines; Sterling Hill specimens are rare.
Manganaxinite is known from a number of specific Franklin assemblages. Additionally, it may form as an accessory mineral in many calcium-silicate assemblages. It is the preferred host for boron in the orebody at Franklin. Among the most important and esthetic Franklin assemblages is one of crusts of bright-yellow manganaxinite crystals which, together with rhodonite, form the vein assemblage which hosts marsturite and ganophyllite; this is described under those species. Manganaxinite and rhodonite also form fine crystals in vuggy seams and veins; contacts with ore are common, and datolite is locally found as younger late-stage coatings.
Much of the less spectacular specimen material occurs as light-yellow druses and crusts and as aggregates in veins and vuggy recrystallized assemblages, associated with andradite, rhodonite, johannsenite, mica, barite, hancockite, willemite, datolite, and other species.
Also found in quantity was a massive variety, light yellow to white, with intense to dull to absent red fluorescence as noted above, and associated with andradite, feldspar, and mica. In massive form, manganaxinite was volumetrically abundant at the north end of the Franklin deposit.
Axinite, undifferentiated as to species, is also found as microcrystals under calcite in veins in the camptonite dikes at Franklin; some of this material has been labeled as titanite.
At Sterling Hill, manganaxinite is a rare mineral. It was found with rhodonite on the 800 level and with epidote, calcite, and heulandite in another assemblage. Among the best Sterling Hill occurrences is one of fine euhedral light-brown crystals, associated with fluorite, epidote, amphibole, scheelite, and calcite on the 1300 level. Both Sterling Hill occurrences were confirmed as manganaxinite by chemical analyses. (Dunn, 1995)

Location Found:

Franklin (Type Locality) and Ogdensburg

Mineral Note:

Manganaxinite renamed with suffix "-Mn" by IMA in 2008.

Year Discovered:

1909

Formula:

Ca₂Mn²⁺Al₂BSi₄O₁₅(OH)

Essential Elements:

Aluminum, Boron, Calcium, Hydrogen, Manganese, Oxygen, Silicon

All Elements in Formula:

Aluminum, Boron, Calcium, Hydrogen, Manganese, Oxygen, Silicon

IMA Status:

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"

Fluorescent Mineral Properties

Shortwave UV light:

Orange-red to red, brightness ranging from very bright to weak

Mid wave UV light:

Orange-red to red, generally weakest of all wavelengths

Longwave UV light:

Orange-red to red, generally weak

Additional Information:

Phosphorescence can be observed under ideal conditions but is extremely weak

To find out more about this mineral at minDat's website, follow this link Axinite-(Mn)

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.415. 'Manganaxinite'

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.43

The Picking Table References

	PT Issue and Page	Description / Comment
View Issue	V. 57, No. 2 - Fall 2016, pg. 12	Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Axinite-(Mn)
View Issue	V. 45, No. 1 - Spring 2004, pg. 12	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 - Manganaxinite
View Issue	V. 33, No. 2 - Fall 1992, pg. 11	The Check List of Franklin-Sterling Hill Fluorescent Minerals - Manganaxinite (Fluorescent Info)
View Issue	V. 20, No. 2 - September 1979, pg. 7	Contributions to the Mineralogy of Franklin and Sterling Hill New Jersey, manganaxinite now Axinite-(Mn) (small article)
View Issue	V. 18, No. 2 - September 1977, pg. 15	The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Manganaxinite now Axinite-(Mn)
View Issue	V. 13, No. 2 - August 1972, pg. 11	The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Axinite (Fluorescent Info)
View Issue	V. 13, No. 1 - February 1972, pg. 10	Franklin Mineral Notes - Axinite
View Issue	V. 10, No. 1 - February 1969, pg. 10	Harvard Research on Franklin Minerals - Axinites
View Issue	V. 7, No. 2 - August 1966, pg. 6	The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Axinite (small article)
View Issue	V. 6, No. 1 - February 1965, pg. 7	Axinite

Images


Axinite-(Mn), margarosanite, willemite, andradite and franklinite from Franklin Mine, Franklin, New Jersey. Collected by Nick Trofimuk, from the collection of Richard C. Bostwick and Tema Hecht, photo by Tema Hecht. 4 ¾" x 3 ½" x 1 ¼" (12 x 9 x 3.3 cm)		Axinite-(Mn), margarosanite, willemite, andradite and franklinite from Franklin Mine, Franklin, New Jersey under shortwave UV light. The axinite-(Mn) fluoresces red, margarosanite pale blue and the willemite green. Collected by Nick Trofimuk, from the collection of Richard C. Bostwick and Tema Hecht, photo by Tema Hecht. 4 ¾" x 3 ½" x 1 ¼" (12 x 9 x 3.3 cm)


Axinite-(Mn) (golden, non-fluorescent), rhodonite (pink), willemite and franklinite from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.


Axinite-(Mn) crystals (golden brown), willemite (white), rhodonite (pink) and franklinite (black) from Franklin, NJ. 3 1/4" x 2 7/8". From the collection of, and photo by Robert A. Boymistruk.		Axinite-(Mn) crystals, willemite, rhodonite and franklinite from Franklin, NJ under shortwave UV light. The axinite-(Mn) fluoresces red and the willemite green, the rhodonite and franklinite are non-fluorescent. 3 1/4" x 2 7/8". From the collection of, and photo by Robert A. Boymistruk.


Axinite-(Mn) crystals (golden), rhodonite (pink) and barite (white) from Franklin, NJ. 2" x 2". From the collection of Zack and Ralph Bonard, photo by WP.