Talc



Talc is a magnesium silicate hydroxide mineral. Local material has not been the subject of many analyses; one specimen contains FeO 1.8, MnO 1.5, and ZnO 6.0 wt. %.
Talc is known from Franklin, Sterling Hill, and the Franklin Marble, but is largely unstudied. The materials earlier described as pyrallolite (Robinson, 1825; Alger, 1845) and steatite (Fowler, 1825) are largely talc.
Local specimens are quite ordinary in appearance, varying from white to gray to light green and other faint colors. The luster is commonly greasy and pearly, but sometimes dull in fine-grained aggregates. The extremely low hardness is a useful though not diagnostic indicator. Talc occurs as massive aggregates, rosettes, and coatings and as pseudomorphs. Few data have been obtained using local material. Franklin talc is fluorescent in ultraviolet, with a light yellowish-white color, more intense in longwave than shortwave. This fluorescent response is best observed on fresh surfaces; it is diminished on surfaces which have been extensively handled.
At Franklin, talc occurs as massive material, commonly associated with calcite and replaces crystals of many species such as spinel, willemite, hemimorphite, and pyroxene. It was reported in massive form in the Buckwheat Dolomite (Palache, 1935). The analytical data given above are for talc which occurs interstitially with nelenite (Dunn and Peacor, 1984). Mamillary masses are known, up to several cm, and may represent replacements of willemite. In the Franklin Marble, talc is host to fine 1-2 cm crystals of quartz. Additionally, it occurs sporadically with calcium silicates in the Franklin Marble. Germine (1987) noted the replacement of Franklin talc by sepiolite.
Talc is found associated with sphalerite, franklinite, and willemite in the north orebody at Sterling Hill. The occurrence has not been studied in detail, but the mineral was common, as was serpentine. Talc replaces red willemite locally at Sterling Hill and might be the unknown mineral of Squiller (1976). It also forms, with serpentine, a thin but visually indiscernible rim on some tephroite crystals, not to be confused with dark brown, very obvious, sonolite rims. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
     
 Formula: Mg3(Si4O10)(OH)2
 Essential Elements: Hydrogen, Magnesium, Oxygen, Silicon
 All Elements in Formula: Hydrogen, Magnesium, Oxygen, Silicon
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
Fluorescent Mineral Properties

 Shortwave UV light: Yellow, moderate brightness
 Mid wave UV light: Yellow, moderate brightness
 Longwave UV light: Yellow, moderate brightness
     
 To find out more about this mineral at minDat's website, follow this link   Talc

     
 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.505

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.79


The Picking Table References
 PT Issue and PageDescription / Comment
V. 58, No. 1 - Spring 2017, pg. 19Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Talc
View IssueV. 33, No. 2 - Fall 1992, pg. 11The Check List of Franklin-Sterling Hill Fluorescent Minerals - Talc (Fluorescent Info)
View IssueV. 27 No. 2 - Fall 1986, pg. 10Minerals of the Franklin Quarry, Philip P. Betancourt, Talc
View IssueV. 18, No. 2 - September 1977, pg. 19The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Talc
View IssueV. 7, No. 2 - August 1966, pg. 13The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Talc (small article)
     
Images

     
Talc, sphalerite, franklinite and willemite from the Sterling Hill Mine, Ogdensburg, NJTalc, sphalerite, franklinite and willemite from the Sterling Hill Mine, Ogdensburg, NJ under longwave UV Light
Talc (light gray green), sphalerite (light redish tan, tan, gray), franklinite (black) and willemite from the Sterling Hill Mine, Ogdensburg, NJ. 4 1/2" x 2 1/4". From the collection of JVF, photo by WP.
Talc, sphalerite, franklinite and willemite from the Sterling Hill Mine, Ogdensburg, NJ under longwave UV light. The talc fluoresces weak dull yellow, sphalerite purple, orange and red, the franklinite and willemite are non-fluorescent. 4 1/2" x 2 1/4". From the collection of JVF, photo by WP.
Talc, sphalerite, franklinite and willemite from the Sterling Hill Mine, Ogdensburg, NJ under midwave UV LightTalc, sphalerite, franklinite and willemite from the Sterling Hill Mine, Ogdensburg, NJ under shortwave UV Light
Talc, sphalerite, franklinite and willemite from the Sterling Hill Mine, Ogdensburg, NJ under midwave UV light. The talc fluoresces weak dull yellow, sphalerite blue, purple, orange, willemite green the franklinite is non-fluorescent. 4 1/2" x 2 1/4". From the collection of JVF, photo by WP.
Talc, sphalerite, franklinite and willemite from the Sterling Hill Mine, Ogdensburg, NJ under shortwave UV light. The talc fluoresces weak dull yellow, sphalerite blue, purple, orange, willemite green the franklinite is non-fluorescent. 4 1/2" x 2 1/4". From the collection of JVF, photo by WP.







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