MIMETITE



Mimetite is a lead arsenate chloride mineral of the apatite group. Franklin material is calcian; Sterling Hill mimetite contains up to 93 mole % of the end-member. Mimetite was reported from Franklin by Rouse et al. (1984). It is also known from Sterling Hill, but is rare locally.
Mimetite is yellow to whitish gray, with adamantine to greasy luster; cleavage is not evident. It occurs as subhedral crystals to several mm and as small masses to several cm. No other physical or optical data exist. Franklin mimetite resembles hedyphane, but the latter is much more abundant. Identification requires chemical analysis and X-ray methods.
Mimetite from Franklin is rare; a specimen occured as yellow-orange, lamellar, 2-cm-thick aggregates in a sheared vein with willemite, amphibole, and calcite in franklinite/calcite ore. It is not visually distinguishable from hedyphane. Sterling Hill mimetite occurs as thin colorless crusts and yellow hemispherules, associated with spessartine, cerussite, and an amphibole similar to hastingsite, in a severely altered augite from the north wall of the Noble Mine at Sterling Hill. Few valid specimens are known. The "pyromorphite" reported from Sterling Hill by Frondel (1972) is this material. In general, yellow material with cerussite on galena is mimetite and not hedyphane. (Dunn, 1995)

 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1832
     
 Formula: Pb5(AsO4)3Cl
 Essential Elements: Arsenic, Chlorine, Lead, Oxygen
 All Elements in Formula: Arsenic, Chlorine, Lead, 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   Mimetite

     
 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.652
The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 34, No. 2 - Fall 1993, pg. 10Duftite From The Sterling Mine Ogdensburg, New Jersey - Mimetite
     
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