THOMSONITE-Ca

Thomsonite is a sodium calcium aluminum silicate hydrate mineral of the zeolite group.
Thomsonite is known from Franklin and Sterling Hill, but is not found in the assemblages in which other local zeolites occur. It was first reported as calciothomsonite Gordon (1923b); this was shown to be thomsonite by Palache (1935). It was also verified from Franklin by Cook (1973). Much material labeled "thomsonite" from Franklin is in fact xonotlite, which occurs in the same assemblage, and is much more abundant. Thomsonite is a very rare mineral locally.
Thomsonite is white to colorless, occurring in clusters of prismatic crystals. The cleavage is perfect, and the luster is vitreous. Thomsonite has a weak white to light yellow fluorescence in both longwave and shortwave ultraviolet (Bostwick, 1982). X-ray diffraction and optical methods are best for distinguishing thomsonite from xonotlite.
Thomsonite has been verified by [Dunn] on one Franklin specimen, on which it occurs as a 2 cm bundle of subparallel, colorless to white, acicular crystals. This is the same specimen verified by Cook (1973) and comes from the part of the mine described by Hurlbut and Baum (1960). Thomsonite occurs in a vug surrounded by prehnite, which is enclosed in a mixture of ganophyllite, unanalyzed mica, and garnet. (Dunn, 1995)

Location Found:

Franklin and Ogdensburg

Year Discovered:

1820

Formula:

NaCa₂[Al₅Si₅O₂₀] · 6H₂O

Essential Elements:

Aluminum, Calcium, Hydrogen, Oxygen, Silicon, Sodium

All Elements in Formula:

Aluminum, Calcium, Hydrogen, Oxygen, Silicon, Sodium

IMA Status:

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

Fluorescent Mineral Properties

Shortwave UV light:

Weak pale yellow, very rare

To find out more about this mineral at minDat's website, follow this link Thomsonite-Ca

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.515. 'Thomsonite'

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.79

The Picking Table References

	PT Issue and Page	Description / Comment
View Issue	V. 58, No. 1 - Spring 2017, pg. 19	Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Thomsonite
View Issue	V. 33, No. 2 - Fall 1992, pg. 11	The Check List of Franklin-Sterling Hill Fluorescent Minerals - Thomsonite (Fluorescent Info)
View Issue	V. 18, No. 2 - September 1977, pg. 19	The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Thomsonite
View Issue	V. 13, No. 2 - August 1972, pg. 13	The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Thomsonite - variety calciothomsonite (Fluorescent Info)

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