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[Roger Warin]

Hello,
It seems important to me to talk about carletonite, this mineral currently flooded in Poudrette quarry, Mont St Hilaire, Quebec.
In addition, the use of the binocular was essential.

[Roger Warin]

The Poudrette Quarry at Mont-Saint-Hilaire in Quebec is a great exception for mineralogists. Alas, this great quarry complex is now drowned.
This alkaline igneous intrusion is not embedded in a mass of silica (quartz) and many very different silicates could have developed, trapping alkaline cations at a high level and also beryllium. The Si and Al concentrations are low. Quartz is missing.
Leifite is a rare but unusual tectosilicate: it forms the leifite group.
Leifite often occurs as fibroradiated aggregates of hexagonal, colorless or greyish prisms.
Such an aggregate (4cm wide) is found at the foot of the main serandite crystal. He is not very photogenic.
The following pictures show the reverse side of a master piece of serandite, of which we do not pay attention to the whitish gangue of feldspars (albite) pierced with black needles of aegirine.

[Roger Warin]

About Poudrette Quarry
I examine again my specimens from Mont St Hilaire, an exceptionally remarkable site, because there is relatively little silicon and so you escape the quartz.
A large sample of analcime from Poudrette Quarry bears crystals of natrolite and rhodochrosite.
On the back side are a few large broken needles of black aegirine (ex acmite). Or arfvedsonite, an amphibole.
While handling the specimen, a small shard broke off. A priori I thought of a burst of rhodochrosite.
In fact, it is a pyroxene, tan in color with strong refractivity and high relief. What is it? I'm thinking aegirine.

[Roger Warin]

Poudrette Quarry, Mont Saint Hilaire, Quebec.
Continuing to explore cabinet-sized specimens, I observed a curious rhodochrosite. Its habit is that of an iron rose. Mindat does not show this aspect, I think.
One question remains: do you confirm the name of the species?

[Tobi]

[Pete Richards]

I concur. This is probably rhodochrosite, which was found often at the Poudrette Quarry, including in this habit. Warm hydrochloric acid on a little flake would confirm that it's a carbonate, and that would about rule out any other alternatives. The most likely alternative would be pyrophanite, which occurs in rosettes but with a much more adamantine luster, and of course is not a carbonate.

[Roger Warin]

Thanks Tobi for your insight. These are also beautiful photos.
Thank you Pete for your comments as always relevant.
Although its molecule is simple, I did not know pyrophanite.
Here are some more photos of leifite, before returning to serandite whose crystals are frequently equant and idiomorphic.
I don't really understand the nature of the driving force that leads to fibroradiated aggregates.

[Roger Warin]

A little perfection in this quite rare assembly:
Serandite, twin on (110).
The 2 twins of serandite have been wonderfully described by Peter Richards.
R.Peter Richards, “Twin laws for serandite from Mont-Saint-Hilaire, Quebec”
Rocks & Minerals, 66, n°1, p. 44 (1991).

The front faces are not in the same plane
The angle is close to 8°.