Augite



Augite is a calcium sodium magnesium silicate mineral of the pyroxene group; samples from Franklin and Sterling Hill contain much Fe, Mn, and Zn. Analyses of the dark, well-formed crystals from Sterling Hill formerly known as jeffersonite show moderately uniform compositions and low sodium contents.
Augite, although validated from both deposits, has been little studied except for the paper by Frondel and Ito (1966b). Jeffersonite was first described and named from Franklin by Vanuxem and Keating (1822a, 1822b); its identity as augite was noted by Troost (1823a), and this relation was further supported by Seybert (1824). A review and morphological description was given by Palache (1935). The preponderance of the material from Franklin and Sterling Hill formerly labeled jeffersonite is augite. Historical notes were provided by Palache (1935).
Frondel and Ito (1966b) described, from Franklin, greenish-black augite as indistinct crystals embedded in pale pink calcite. This augite has a density of 3.55 g/cm3 and a well developed parting; Palache (1935) described it occurring in platy masses.
At Franklin, augite has been reported associated with pink calcite (Frondel and Ito, 1966b), and herein with rhodonite. Little is known of the assemblages of augite from Franklin, but Palache (1935) noted it at the Trotter Mine and the Parker Mine.
Augite from Sterling Hill, however, has a well-documented literature, in which it is largely referred to as jeffersonite. Most of the black-surfaced, well-formed crystals collected at the open pits at Sterling Hill, and referred to in the literature as jeffersonite, are augite. This material, some occurring as enormous crystals to 30 cm, was locally abundant and was collected over a period of many years, as recently as the 1970's. The crystals are invariably blackish brown; the coating is likely one of Mn-oxides, but has not been studied. These augite crystals are associated with well-crystallized fayalite, gahnite, spessartine, and apatite and with other species such as galena and sphalerite. Some crystals have been completely altered to a pith-like mixture called anomalite by Koenig (1879) and mentioned by Palache (1935). Magnesian hastingsite is common as oriented overgrowths of tiny lustrous blackish crystals on these augite crystals. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
     
 Formula: (Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
 Essential Elements: Calcium, Magnesium, Oxygen, Silicon
 All Elements in Formula: Aluminum, Calcium, Iron, Magnesium, Oxygen, Silicon, Sodium, Titanium
     
 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   Augite

     
 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.431

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.43


     
Images

     
Augite crystals in calcite with minor willemite from the Sterling Hill Mine, NJAugite crystals in calcite with minor willemite from the Sterling Hill Mine, NJ under shortwave UV Light
Augite crystals (black) in calcite with minor willemite from the Sterling Hill Mine, NJ. From the collection of, and photo by JVF.
Augite crystals in calcite with minor willemite from the Sterling Hill Mine, NJ under shortwave UV light. The calcite fluoresces orange-red and willemite green, the augite is non-fluorescent. From the collection of, and photo by JVF.


Augite crystals from Sterling Hill, New Jersey.
Augite crystals from Sterling Hill, New Jersey. From the collection of and photo by Ken Reynolds.


Augite crystals from the Sterling Hill Mine, Ogdensburg, NJ
Augite crystals from the Sterling Hill Mine, Ogdensburg, NJ. 3 1/4" x 4". From the collection of JVF, photo by WP.







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