Mineral notes:

Yellow zircons and pyrochlores from Morocco

by Tomasz Praszkier

   High Atlas in Morocco is vastly built by Mesozoic sedimentary rocks (mosty Jurassic and Cretaceous age) with numerous small syenite intrusions in the central part of the massife. Pegmatites and contact metamorphic rocks connected with those intrusions are the source of many interesting mineral specimens. Usually those mineral-rich zones are very small, and they disappear as quick as the show up. The best known species from the area are apatites, titanites, prehnites, magnetites, garnets, pyroxenes and amphiboles.

   One of the most „classic” location in High Atlas is Tizi n'Inouazane (Tizi-n-Inouzane) pass, located about 30 km from Imilchil, with beautiful landscapes 360° around. The system of intrusions with pegmatites and metasomatic zones that occurs there has been a source of gemmy apatites and other minerals for decades. The most famous and heavily dug zone is located on the northern slopes of the ridge, next to the pass. This is the place from where the very gemmy (usually isolated) apatites, characterised by vivid yellow/green color and great luster, come from. Not far from there an interesting small find took a place in the mid 2022 …
   In the central part of the pass a small pocket with aegirines on microclines with associated magnetites and andradites was discovered. This paragenesis is typical for the area, but there was also the unusual presence of titanites, two genereation of zircons, chamosites and what is most interesting - pyrochlores (fluorcalciopyrochlore). This is the first time when pyrochlore specimens of collectors quality (although still very small) are described from Morocco. Pocket yield a few hundreds specimens (mostly low quality), including a few dozens containing yellow zircons and pyrochlores.

   Aegirine crystals from that find were of dark green to balck color, usually corroded. Their size varied usually between 3 and 7 cm, and most of them were broken off from the original matrix. They are characterised by quite well developed prism faces. Some crystals are twinned and some show skeletal growth.

   Andradite formed as grey, almost black, dodecahedral crystals, in size up to 1 cm, growing on aegirine or microcline.

   Chamossite (chlorite) formed dark grey spheroidal clusters, weathered on the surface, up to 1 cm in diameter, usually growing on aegirine.

   Fluorcalciopyrochlore is quite common in the find and is observed (in our material) uniquely on aegirine crystals. Pyrochlore crystals are unfortunately quite tiny, reaching up to 3 mm. They are always very lustrous and formed as simple brown octahedrons. They are frequently scattered on aegirines, together with yellow zircons and titanites.

   Microcline in the find shows tabular habit, formed as well developed, a few cm big crystals, in ecru color. They form clusters on which aegirine and other minerals grow.

   Magnetite is present in two generations. Older, more complex dodectahedral crystals are quite heavily etched, with no luster. Younger generation magnetite is formed as classic black metalic octahedrons, in size usually less than 1 cm, sometimes up to 2-3 cm, and with quite good luster. 

   Titanite was quite common in the pocket. It is developed as quite well formed, lustrous, brown elongated crystals, grouped in fan shape clusters. They usually grow on the aegirines. Size of the clusters rarely exceeds 8 mm.

   Zircon in the find occured in two „types”, both in very simple „classic tetragonal” forms, with prism and single dipyramide. First type is formed as brownish crystals, with very short prism and dominating pyramids. Size of this type of crystals reaches up to 7-8 mm. They are visually not very attractive. Second habit of the zircons is characterised by very high luster and much better developed prisms with smaller pyramids. However the most distinctive feature of the second habit is very bright yellow color, creating a great contrast on the dark aegirines. Quite frequently zircon crystals are also doubly terminated. Size of the yellow zircons reaches up to 8 mm.

   The best specimens from the find were aegirine crystals overgrown by scattered lustrous bright yellow zircons and brown octahedrons of the fluorcalciopyrochlore. Unfortunately due to the weathering and the way the specimens were collected and transported most of them are damaged.

Map of Morocco with marked location of the zircons and pyrcholores occurence.

Geology of the Central part of High Atlas with location of the Tizi n'Inouazane - zircon location.

Tizi n'Inouazane – pass in High Atlas where small pocket with zircons and pyrochlores was found. Spirifer Minerals photo.

View from the workings at Tizi n'Inouazane pass in High Atlas. Spirifer Minerals photo.

Aegirine crystal with yellow zircons. Specimen's size 5.1 cm. Spirifer Minerals photo.

Andradite crystal (diameter about 1 cm) with magnetite, zircons and pyrochlores, growing on aegirine. Spirifer Minerals photo.

Chamossite spheroidal cluster (diameter about 1 cm) with zircons and titanite, growing on aegirine. Spirifer Minerals photo.

Brown fluorcalciopyrochlore octahedral crystals with zircons and microcline, growing on aegirine. Spirifer Minerals photo.

Brown fluorcalciopyrochlore octahedral crystals with zircons and microcline, growing on aegirine. Spirifer Minerals photo.

Brown fluorcalciopyrochlore octahedral crystals with zircons and magnetite, growing on aegirine. Spirifer Minerals photo.

Brown fluorcalciopyrochlore octahedral crystals growing on aegirine. Spirifer Minerals photo.

10 cm specimen of tabular microcline crystals with yellow zircons and magnetite. Spirifer Minerals photo.

Magnetite with yellow zircons growing on microcline. Spirifer Minerals photo.

Small magnetite with yellow zircons and brown pyrochlores growing on aegirine, with microcline. Specimen's size 5.3 cm. Spirifer Minerals photo.

Cluster of brown titanite crystals and yellow zircons growing on aegirine. Specimen's size 2.7 cm. Spirifer Minerals photo.

Group of the bright yellow zircon crystals growing on aegirine. Field of view 2 cm. Spirifer Minerals photo.

Bright yellow zircon crystals (some doubly terminated) growing on aegirine. Field of view 2.5 cm. Spirifer Minerals photo.