MICROCLINE

Microcline, a potassium aluminum silicate mineral of the feldspar group, was first verified from Franklin by Kemp (1893a) and is surely the "green feldspar" reported by Nuttall (1822). Some material has been called amazonstone or amazonite. Microcline was reported by Palache (1935) as large crystals at Sterling Hill and also as a common constituent of the local pegmatites, in crystals to 30 cm. Peters et al. (1983) reported and illustrated microcline from the Buckwheat Dolomite. Frondel et al. (1966), in an extensive study of the Franklin feldspars, found 2/3 of the 59 studied specimens to be microcline or sodian anorthoclase, having BaO values from nil to approximately 3.0 wt. %. A survey by Langer (1994) found the trace-element composition ranges of three specimens of green microcline to be: Rb 202-327, Pb 938-2547, Ba 1699- 6808, and Zn 507-830 ppm. The colorless to white feldspar associated with the lead silicates is largely microcline (Dunn, 1985b); it is Pb-free at the microprobe level. A barian microcline from Sterling Hill was reported by Frondel et al. (1966).
Much of the common green feldspar found at Franklin, especially on the Trotter dump, is perthitic microcline. This green microcline, when in contact with calcite, occurs in fine euhedral crystals up to 30 cm, as figured by Palache (1935); [Dunn] has seen crystals up to 7 cm, but the preponderance of local microcline is massive.
Franklin microcline also occurs in yellow-brown, olive-green, and pale white, as well as a very bright green color. Local microclines may fluoresce with a weak red or moderate blue color under shortwave ultraviolet.
Microcline is one of very few minerals associated with quartz, an uncommon mineral locally. It is also associated with rhodonite, allanite, andradite, calcite, franklinite, diopside, and rarely willemite or bustamite. In addition to occurrences in association with pegmatite, microcline is found in the calcium silicate units of the Franklin orebody. The pseudomorphs after possible microcline, described by Palache (1935), are discussed herein under pumpellyite. Microcline was reported from Sterling Hill by Jenkins (1994). (Dunn, 1995)

Location Found:

Franklin and Ogdensburg

Mineral Note:

Most common feldspar at Franklin and Sterling Hill. Bright green microcline is commonly called "amazonite". Hyalophane is another variety, and was once on the Franklin Mineral Species List, some specimens fluoresce a deep red under shortwave UV light.

Year Discovered:

1830

Formula:

KAlSi₃O₈

Essential Elements:

Aluminum, Oxygen, Potassium, Silicon

All Elements in Formula:

Aluminum, Oxygen, Potassium, Silicon

IMA Status:

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"

Fluorescent Mineral Properties

Shortwave UV light:

Blue, moderate to weak brightness, weak to very weak red

To find out more about this mineral at minDat's website, follow this link Microcline

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.510

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.68

The Picking Table References

	PT Issue and Page	Description / Comment
View Issue	V. 58, No. 1 - Spring 2017, pg. 13	Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Microcline
View Issue	V. 41, No. 1 - Spring 2000, pg. 14	A Scheelite-bearing Assemblage From Franklin, New Jersey By Robert E. Jenkins II - Microcline
View Issue	V. 35, No. 1 - Spring 1994, pg. 22	Geology and Mineralogy of a Veinlet Assemblage Associated With Wollastonite-Bearing Rocks, Sterling Mine, Ogdensburg, New Jersey, Robert E. Jenkins II - Microcline
View Issue	V. 33, No. 2 - Fall 1992, pg. 11	The Check List of Franklin-Sterling Hill Fluorescent Minerals - Microcline (Fluorescent Info)
View Issue	V. 24 No. 2 - Fall 1983, pg. 15	Minerals of the Buckwheat Dolomite Franklin, New Jersey, Microcline (small description)
View Issue	V. 18, No. 2 - September 1977, pg. 16	The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Microcline
View Issue	V. 13, No. 2 - August 1972, pg. 12	The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Microcline (Fluorescent Info)

Images


Microcline and minor franklinite from the Franklin Buckwheat Dump, Franklin, NJ. Photo by WP.		Microcline and minor franklinite from the Franklin Buckwheat Dump, Franklin, NJ under shortwave UV light. The microcline fluoresces light blue and pink, franklinite is non-fluorescent. Photo by WP.


Microcline var amazonite (green), calcite (white), salmon calcite (pink), franklinite (black) and garnet (brown) from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.		Microcline var amazonite, calcite, salmon calcite, franklinite and garnet from Franklin, NJ under shortwave UV light. The calcite and salmon calcite fluoresces orange-red, the amazonite, franklinite and garnet are non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


Microcline var amazonite (green), calcite (white), and willemite (tan) from Franklin, NJ. From the collection of, and photo by WP.		Microcline var amazonite, calcite and willemite from Franklin, NJ under shortwave UV light. The amazonite fluoresces gray, calcite orange-red and the willemite green, the franklinite is non-fluorescent. From the collection of, and photo by WP.