CAHNITE



Cahnite is a calcium boron arsenate hydroxide mineral. Cahnite was first announced by Palache (1921) and described from Franklin by Palache and Bauer (1927b); it has not been found at Sterling Hill. The crystal structure is similar to those of xenotime and zircon. Cahnite is known primarily in colorless crystals, which are pseudo-tetrahedral or pseudo-octahedral in habit, but is most commonly found complexly twinned. Most crystals are 1-2 mm or less in size, but crystal twins up to 18 mm are known (Palache, 1935).
Cahnite is colorless to white or light-yellow; Frondel (1972) has reported light green material. It is transparent and has a vitreous luster, and a density of 3.156 g/cm3. Optically, it is uniaxial, positive, with very low birefringence.
Cahnite fluoresces in longwave and shortwave ultraviolet with a moderate yellowish white color. When massive, it can be confused with barite, but is easily distinguished by its unique cleavage or by using optical or X-ray methods. Additional descriptive information was given by King (1993).
Cahnite was found in superb crystals in a number of assemblages from the Parker Mine. Palache and Bauer (1927a) reported it occurring with manganaxinite, barite, and friedelite and also with calcite, willemite, friedelite, and barite.
Palache and Bauer (1927a) also reported a 1927 find with manganaxinite, calcite, rhodonite, barite, hedyphane and willemite, these minerals being followed in sequence of formation by cahnite and finally datolite.
Cahnite may be much more common than previously recognized; it is found sparingly with a number of rare minerals in vein assemblages.
A number of unique assemblages are known. Cahnite occurs with samfowlerite on a light pink, lustrous, rough-surfaced, unstudied garnet which lines vugs in franklinite; the twinned 1 mm crystals resemble those of Palache (1935). Cahnite of pseudo-octahedral habit occurs in vugs in brown andradite, associated with hetaerolite, hausmannite, groutite, and kentrolite. Cahnite was reported by Cook (1973) from the Buckwheat Dump, associated with andradite, flinkite, and "carminite" (later found to be jarosewichite). Cahnite is also associated with a druse of hodgkinsonite on franklinite-willemite ore, and Frondel (1972) has reported it in cleavable 25 mm masses with roeblingite. It is also known from vugs in light green andradite, associated with mica and copper. (Dunn, 1995)

 Location Found: Franklin (Type Locality)
     
 
 Year Discovered: 1921
     
 Formula: Ca2[B(OH)4](AsO4)
 Essential Elements: Arsenic, Boron, Calcium, Hydrogen, Oxygen
 All Elements in Formula: Arsenic, Boron, Calcium, Hydrogen, Oxygen
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
Fluorescent Mineral Properties
 Shortwave UV light: Moderately weak cream
 Mid wave UV light: Moderately weak cream
 Longwave UV light: Moderately weak cream
 Additional Information: Phosphoresces moderately weak cream
     
 To find out more about this mineral at minDat's website, follow this link   Cahnite

     
 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.660

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.47
The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 57, No. 2 - Fall 2016, pg. 14Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Cahnite
View IssueV. 34, No. 1 - Spring 1993, pg. 11The Flinkite / Cahnite / Jarosewichite Assemblage From Franklin, New Jersey, Vandall T. King - Cahnite
View IssueV. 33, No. 2 - Fall 1992, pg. 10The Check List of Franklin-Sterling Hill Fluorescent Minerals - Cahnite (Fluorescent Info)
View IssueV. 18, No. 1 - March 1977, pg. 21The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Cahnite
View IssueV. 9, No. 1 - February 1968, pg. 11The Exclusive Minerals of Franklin/Ogdensburg, N.J. (as of January 1968) by Frank Z. Edwards - Cahnite
View IssueV. 2, No. 1 - February 1961, pg. 5Crystal Structure of Cahnite (small article)
     
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