FORSTERITE



Forsterite, a magnesium silicate mineral of the olivine group, is rare at Sterling Hill and unknown from Franklin. Francis (1980) described Sterling Hill forsterite occurring as < 0 5 mm light-brown blebs with franklinite crystals and massive zincite in a calcite matrix; willemite is present as traces. Forsterite also occurs as 1-2 mm pinkish-brown crystals with phlogopite and calcite and was reported by Squiller (1976) from the outer zincite zone at Sterling Hill. A manganoan forsterite associated with franklinite was reported from the Sterling Hill east-limb surface exposure, at approximately 500 N; the composition of this material is approximately (Mg0.93MnO0.80 Zn0.24Fe0.03) SiO4 (Johnson, 1990). A Sterling Hill replacement assemblage which included forsterite, clinohumite, chondrodite, humite, dolomite, and calcite was reported by Johnson (1990) from marble above the east limb, about 5 cm from the ore-contact. The composition of this material, very close to the end-member, is approximately (Mg1.74Zn0.17Fe0.10Mn0.02)SiO4. (Dunn, 1995)

 Location Found: Ogdensburg
     
 
 Year Discovered: 1824
     
 Formula: Mg2SiO4
 Essential Elements: Magnesium, Oxygen, Silicon
 All Elements in Formula: Magnesium, Oxygen, Silicon
     
 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   Forsterite

     
 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.336
     
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