Ferroceladonite is a rare mineral. Apart from MSH, and the Demix-Varennes and Montréal-Est quarries, all in the Montérégian Hills of Québec, it has been reported from only a half-dozen other localities. (Had it not been for a lack of enthusiasm, MSH might well have been the TL – but it isn’t.)

At MSH, ferroceladonite is both rare and plentiful. It is not found very often, but when found it often covers everything in sight. This specimen is somewhat unusual in that the ferroceladonite appears to be a replacement of aegirine and, moreover, is more than just a thin coating as is often the case.

The first two photos (FOV 6.9 x 4.6 mm) show part of an aegrine crystal replaced mostly by ferroceladonite with a few tiny plates of albite. In this case, most of the “filling” of the aegirine pseudomorph has fallen out.

The second pair of photos (FOV 6.3 x 4.1 mm) shows a similar aegirine pseudomorph except that the “filling” is mostly intact. (I don’t know what the brown grungy stuff is.)

The third pair of photos (FOV 6.6 x 4.3 mm) shows a small cavity (not a pseudomorph), thickly packed with ferroceladonite. The white platy crystals are (probably) albite.

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