Groutite



Groutite is a manganese oxide hydroxide mineral. The material described by Klein and Frondel (1967) is antimonian; they gave the composition as Sb2O5 7.6, Mn2O3 80.9 wt. %. [Dunn’s] analysis of this material yielded Mn2O3 79.8, SiO2 0.4, Fe2O3 0.5, MgO 1.4, ZnO 1.3, Sb2O5 5.5, with H2O 11.1 by difference, total = 100 wt. %. The more common prismatic groutite is Sb-free with composition Mn2O3 88.6, Fe2O3 0.5, MgO 0.6, ZnO 0.4, H2O 9.9 by difference, total = 100.0 wt. %.
Groutite was first reported from Franklin by Klein and Frondel (1967) and Klein (1968). Specimens were commonly mislabeled manganite, and Palache (1935), in his description of manganite, an exceedingly rare mineral locally, may have examined groutite; the matter is unresolved. Groutite has not been reported from Sterling Hill.
Groutite occurs in two distinct habits. The first of these, reported by Klein and Frondel (1967), occurs as platy, irregular, bladed, opaque 0.5 mm crystals, black, with strong reddish-brown internal reflections and perfect cleavage. This groutite is rare; only one specimen is known. The more common groutite is strongly prismatic in habit, opaque, and black. Groutite also occurs as dense mats of thin acicular reddish-brown crystals. It is best identified using X-ray diffraction techniques.
The antimonian groutite reported by Klein and Frondel (1967) occurs in an open seam in green andradite, associated with manganite, cahnite, romeite, franklinite, and a Ca-As apatite.
The groutite represented in local and systematic collections is of a distinctly different paragenesis and occurs as superb crystals in vugs in a distinctly brown andradite associated with brown willemite. The vugs have formed by the dissolution of barite, leaving rectangular, relict, inherited networks of fine-grained hetaerolite. Hetaerolite is the most common mineral lining such vugs. Hausmannite, manganite, calcite, kentrolite, and cahnite are also associated minerals. Much local groutite from this assemblage has been mislabeled manganite (Dunn, 1987). (Dunn, 1995)


 Location Found: Franklin
     
 
 Year Discovered: 1945
     
 Formula: Mn3+O(OH)
 Essential Elements: Hydrogen, Manganese, Oxygen
 All Elements in Formula: Hydrogen, Manganese, Oxygen
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
     
 To find out more about this mineral at minDat's website, follow this link   Groutite

     
 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.593

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.59


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 28, No. 2 - Fall 1987, pg. 5Kentrolite, Groutite, Manganite, and Hausmannite From Franklin, New Jersey: Some Observations, Dr. Pete J. Dunn, Groutite, Manganite, Hausmannite
View IssueV. 15, No. 1 - February 1974, pg. 8Mineral Notes - Groutite (small article)
View IssueV. 9, No. 1 - February 1968, pg. 8Mineralogical Data - Antimonium Groutite
View IssueV. 9, No. 1 - February 1968, pg. 11The Exclusive Minerals of Franklin/Ogdensburg, N.J. (as of January 1968) by Frank Z. Edwards - Antimonian Groutite
     
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