Norbergite



Norbergite is a magnesium silicate fluorine hydroxide mineral of the humite group and the most fluorine-rich member of the group. As noted by Jones (1969), there is very little solid-solution of cations substituting for Mg; the known analyses agree well with the theoretical composition. Norbergite, alone among the humites, has no known analogue in either the manganese-humite or the leucophoenicite groups. Such an analogue may be precluded crystallochemically. The verified brown and orange norbergites have not been chemically analyzed; their color may be due to iron or manganese substitution.
The best euhedral crystals of Franklin norbergite were reported from the Nicoll Quarry at the turn of the century and subsequently described by Larsen et al. (1928); the early history is given by Palache (1935). Nicoll Quarry norbergite was also used by Taylor and West (1929) and Gibbs and Ribbe (1969) for the determination and refinement, respectively, of the crystal structure. Norbergite is a mineral of the Franklin Marble.
Although fine crystals may attain 2-3 cm, most local norbergite occurs as anhedral to subhedral 1-4 mm grains in the host marble. Local crystals can be of very high quality; White and Hyde (1982a), using TEM techniques, examined two specimens from Franklin and found them to be perfect crystals. Generally, at least for the well-studied specimens, norbergite is light yellow or light greenish-yellow; however, well-formed 1 cm brown crystals are known. Some samples, carefully verified as norbergite, are visually indistinguishable from common orange-brown chondrodite; the distinction is best made with X-ray diffraction methods. The luster is vitreous; the cleavage is imperfect; and the density is 3.20 g/cm3.
The fluorescence in ultraviolet for Nicoll Quarry samples is yellow in shortwave and weak yellow to absent in longwave. Anhedral microcrystals of apatite and/or uvite may resemble norbergite.
Norbergite specimens from the Nicoll Quarry in the Franklin Marble in Franklin have been used for all the major investigations, and it is recommended that they be used for future studies as well. In 1905 another occurrence of norbergite was found by Palache (1935) in the Nicoll Quarry associated with black spinel, pyrrhotite, and fluorite. Fine, yellow, euhedral norbergite crystals, up to 25 mm in clusters to 3 x 2 x 2 cm, were found in the Franklin Quarry in 1982 and have the tabular habit figured by Palache. In this occurrence, norbergite is associated with calcite, hercynite, and phlogopite. Norbergite has also been reported from the Fowler Quarry and likely occurs sporadically in many of the other local marble quarries. It also occurs in marble on the 800 level of the Sterling Mine as brownish rims surrounding gray material; both have been verified as norbergite. Norbergite crystals were reported by Larsen et al. (1928) to have cores of chondrodite. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1926
     
 Formula: Mg3(SiO4)(F,OH)2
 Essential Elements: Fluorine, Magnesium, Oxygen, Silicon
 All Elements in Formula: Fluorine, Hydrogen, Magnesium, Oxygen, Silicon
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
Fluorescent Mineral Properties

 Shortwave UV light: Bright to weak yellow
 Mid wave UV light: Weak yellow
     
 To find out more about this mineral at minDat's website, follow this link   Norbergite

     
 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.345

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.70


The Picking Table References
 PT Issue and PageDescription / Comment
V. 58, No. 1 - Spring 2017, pg. 14Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Norbergite
View IssueV. 45, No. 1 - Spring 2004, pg. 13The 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 - Norbergite
View IssueV. 33, No. 2 - Fall 1992, pg. 11The Check List of Franklin-Sterling Hill Fluorescent Minerals - Norbergite (Fluorescent Info)
View IssueV. 27 No. 2 - Fall 1986, pg. 7Minerals of the Franklin Quarry, Philip P. Betancourt, Norbergite
View IssueV. 13, No. 2 - August 1972, pg. 12The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Chondrodite/Norbergite (Fluorescent Info)
View IssueV. 10, No. 2 - August 1969, pg. 10Mineral Notes - Norbergite
View IssueV. 8, No. 2 - August 1967, pg. 6Mineralogical Data - Norbergite
     
Images

     
Norbergite from Braen Stone Industries' Franklin QuarryNorbergite from Braen Stone Industries' Franklin Quarry under shortwave UV Light
Norbergite (yellow-cream) from Braen Stone Industries' Franklin Quarry. Photo by JVF.
Norbergite from Braen Stone Industries' Franklin Quarry under shortwave UV light. The norbergite fluoresces yellow. Photo by JVF.


Norbergite vein from Braen Stone Industries' Franklin QuarryNorbergite vein from Braen Stone Industries' Franklin Quarry under shortwave UV Light
Norbergite vein (yellow-cream) from Braen Stone Industries' Franklin Quarry. Photo by JVF.
Norbergite vein from Braen Stone Industries' Franklin Quarry under shortwave UV light. The norbergite fluoresces yellow. Photo by JVF.







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