Powellite



Powellite, a calcium molybdate mineral and the molybdenum analogue of scheelite, occurs at both Franklin and Sterling Hill. It is commonly colorless to very light greenish-yellow with greasy to adamantine luster and fluoresces with a moderate yellow color in shortwave ultraviolet and a weaker yellow in longwave. It occurs as alterations of molybdenite crystals at both deposits.
At Franklin, powellite is associated with microcline, willemite, apatite, molybdenite, and calcite, in a light-colored rock. Semiquantitative analysis of two specimens from this Franklin occurrence yielded, respectively and approximately, CaO 24 and 23 wt. %, WO3 31 and 43 wt. %, and MoO3 41 and 31 wt. %, showing that this material has Mo > W in both specimens and is a tungstenian powellite. A possibly distinct assemblage of powellite with scapolite and molybdenite has also been found on the Buckwheat Dump.
At Sterling Hill, powellite occurs in several assemblages. It is found with epidote and sphalerite on a thin vein in gneiss. Semiquantitative analysis of this material yielded a composition of approximately CaO 25 wt. %, WO3 29 wt. %, and MoO3 44 wt. %. It was also found with hedenbergite, molybdenite, calcite, and red-fluorescing feldspar in the hanging wall of the black-willemite ore on the 430 level; this material has not been chemically analyzed by [Dunn]. In 1990, powellite with 70 mole % of the end-member was found on the 340 level at Sterling Hill with wollastonite (P. Modreski, pers. comm.). (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1891
     
 Formula: Ca(MoO4)
 Essential Elements: Calcium, Molybdenum, Oxygen
 All Elements in Formula: Calcium, Molybdenum, Oxygen
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
Fluorescent Mineral Properties

 Shortwave UV light: Bright to moderately bright yellow
 Mid wave UV light: Bright to moderately bright yellow
 Longwave UV light: Bright yellow
 Additional Information: Weaker fluorescence in longwave
     
 To find out more about this mineral at minDat's website, follow this link   Powellite

     
 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.644

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.71


The Picking Table References
 PT Issue and PageDescription / Comment
V. 58, No. 1 - Spring 2017, pg. 15Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Powellite
View IssueV. 33, No. 2 - Fall 1992, pg. 11The Check List of Franklin-Sterling Hill Fluorescent Minerals - Powellite (Fluorescent Info)
View IssueV. 18, No. 2 - September 1977, pg. 17The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Powellite
View IssueV. 13, No. 2 - August 1972, pg. 12The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Powellite (Fluorescent Info)
View IssueV. 13, No. 1 - February 1972, pg. 10Franklin Mineral Notes - Scheelite/Powellite
View IssueV. 3, No. 2 - July 1962, pg. 6Powellite
View IssueV. 3, No. 1 - February 1962, pg. 6Powellite (small article)
     
Images

     
Powellite, calcite, franklinite and minor quartz from the Sterling Hill Mine, NJ.Powellite, calcite, franklinite and minor quartz from the Sterling Hill Mine, NJ. under midwave UV Light
Powellite (light to dark brown), calcite (white to beige), franklinite (black) and minor quartz (light gray) from the Sterling Hill Mine, NJ. Photo by WP.
Powellite, calcite, franklinite and minor quartz from the Sterling Hill Mine, NJ under mid-wave UV light. The powellite fluoresces yellow and calcite red, the franklinite and quartz are non-fluorescent. Photo by WP.
Powellite, calcite, franklinite and minor quartz from the Sterling Hill Mine, NJ. under shortwave UV Light
Powellite, calcite, franklinite and minor quartz from the Sterling Hill Mine, NJ under shortwave UV light. The powellite fluoresces light yellow and calcite red-orange, the franklinite and quartz are non-fluorescent. Photo by WP.







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