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Willhendersonite (micro crystals)
K0-1Ca1.5-1.0[Al3Si3O12]·5H2O triclinic
Willhendersonite is a zeolite group mineral whose crystals are almost always less than a mm.
Willhendersonite
Italy
Vispi Quarry, near the town of San Venanzo, Province of Terni, Umbria, Italy.
The best locality appears to be the Vispi Quarry where trellis like twinned aggregates of white crystals up to about 3 mm. are found. “…very characteristic twinned specimens which have a very striking appearance. …the twinned aggregates (width are less than 1.0 mm in diameter) consist of crystals in three different orientations, each with faces approximately perpendicular to those of the others and arranged in most specimens to have a “trellis-like” appearance.”
1 Willhendersonite is often intergrown with radiating sprays of colorless phillipsite. Found with and formed after them are colorless spheres of thomsonite and white frosted but translucent anhedral apophyllite. Some specimens grow in vugs lined or partially lined with well-formed crystals of brown phlogopite. Melilite and other minerals are also found on some specimens. The minerals are found in vugs in quarternary basic potassic basalts. The mineral is fairly abundant in the quarry, or at least was at one time and I think that everyone who wanted a specimen of the mineral could get one for a reasonable price (less than $50). It doesn’t take but a few hundred specimens of a micro white zeolite to saturate the market. However the number of minerals associated with willhendersonite at this locality and their well crystallized nature means that micromounters will be happy to have a number of different specimens from this locality, each showing different associations. Just looking at the two specimens in my collection makes me realize I could probably find at least a half dozen more that I would not mind having.
1. Willhendersonite, a new zeolite isostructural with chabazite, Donald R. Peacor, Pete J. Dunn, William B. Simmons, Ekkehart Tillmanns and Reinhard X. Fisher; American Mineralogist, Volume 60, pages 186-189, 1984.
Willhendersonite
Germany
Rhineland-Palatinate, Eifel Mts., Mayen, Ettringen, Ettringer Belleberg Mt.
The willhendersonite found near Mayen is described as “…clear well-formed crystals averaging 60x30x20 μm in cavities in a limestone xenolith from a basalt associated with gismondine, chabazite, phillipsite, thomsonite, ettringite and thaumasite.”
1
1. Willhendersonite, a new zeolite isostructural with chabazite, Donald R. Peacor, Pete J. Dunn, William B. Simmons, Ekkehart Tillmanns and Reinhard X. Fisher; American Mineralogist, Volume 60, pages 186-189, 1984.
[Rock Currier 6 November 08]
Edited 13 time(s). Last edit at 05/03/2009 03:02AM by Rock Currier.
