The beryl occurs in the Guerioune granitic complex mostly in K-feldspar-quartz-zinnwaldite and beryl pegmatites, at the contact with leucocratic muscovite-granite. The beryl occurrences are mainly located at the northwestern edge of the massif. Beryl can also be found in centimetric pegmatitic pockets located in the pink biotite granites and porphyric biotite granites). They can show different aspects: (a) big crystals up to several centimeters length in pegmatites; they are associated with big crystals of quartz, zinnwaldite and potassium feldspars; (b) space filling (miarolitic cavities) with the same mineralogical association but crystal’s size is less than one-centimeter length; (c) fine green beryl in rare centimetric pegmatite veinlet; and (d) as small crystals lining the walls of open cavities in the pink biotite granite. Beryl Crystals of beryl were mostly collected from the northwestern part of the Guerioune massif, in the non-outcroping granitic pegmatite where beryl crystals are (particularly) abundant. The beryl is either included in quartz or in assemblages showing quartz, zinnwaldite, and K-feldspar. It can be found as isolated crystal at the surface or in alluvial sediments. Other beryls were collected from “pockets and nests” located in granites (pink, porphyric, and rare albitic granite). They are associated to quartz–zinnwaldite lining the miarolitic cavities and form small centimetric pockets. In intra-granitic pegmatite, the beryl crystals are surrounded by the Li-micas zinnwaldite.

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References