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GeneralAlmandine Garnet crystals growing in Pockets in Hydrothermal Veins

14th Feb 2018 18:58 UTCTony Albini

Hi Everyone,

The Becker quarry in West Willington, Connecticut, USA has produced almandine garnet crystals that grew in hydrothermal veins that started in depths of the Earth's crust. Dr. Jay Ague of Yale University wrote a paper on this quarry. Mindat photo ID number 537938 shows one of these garnets. Pocket almandines seem to be a rare paragenesis of this species. Spessartines and other garnet species readily occur in pockets. Has anyone seen pocket growth almandines elsewhere? All responses are appreciated.

Regards,

Tony Albini

15th Feb 2018 01:30 UTCCharlie Smith

The only literature I could find on the internet concerning Almandine found in a hydrothermal vein was this paper, which describes a grain of almandine found in a hydrothermal vein in New Zealand. It also mentions some other localties where almandine was foud in other hydrothermal systems. I hope this helps,

Charlie Smith

15th Feb 2018 02:00 UTCStephen Turner

I have several vein almandines in my collection eg. from Serrate Redondo, Paraiba in Brazil (in quartz) and Kamiaba, Katanga, DRC (in calcite) - there are photos in Mindat.

Steve

15th Feb 2018 15:59 UTCTony Albini

Hi Charlie and Stephen, thanks for the information.

This site mentioned above is the only one I knew for almandine occurring in pockets. All the granite pegmatite mines and metamorphic localites I field collected had the almandine imbedded in the matrix, not free, pocket crystals. Have either of you ever seen these in a granite pegmatite? I have a floater garnet labelled from Shigar Vally in Pakistan as just garnet, do not know if is spessartine ar almandine.

16th Feb 2018 20:53 UTCClifford Trebilcock

Hi Tony,

Last summer 2017 we collected several etched gemmy almandine fragments from a pocket of albite,quartz and mica at the Fisher Quarry pegmatite in Topsham, Maine. They were dark orange/red and very similar to the etched spessartine from Navedadora Claim in MG, Brazil except smaller. There were larger masses of normal almandine nearby. Some of the fragments even have tiny quartz crystals attached. Not analyzed but the smallest pieces can be picked up by a strong magnet. I think that would indicate higher Fe content instead of manganese.

A few years ago I also found several small, very dark red, almandine crystals with etched faces at the Square Pit about 1/2 mile north of the Fisher Quarry. These were found in albite vugs with fine grained dark green mica. These etched crystals are also attracted to a strong magnet. I too have

seldom seen almandine crystals in pockets in pegmatites here in the northeast US.

Cliff Trebilcock

16th Feb 2018 21:36 UTCTony Albini

Cliff, thanks for adding this information for all of us.

Tony Albini

20th Feb 2018 16:05 UTCTony Albini

From the comments from everyone, it appears that almandine garnets forming in pockets in any mineral environment is rare.

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