TFB93XXX: Very compact group of Biotite crystals, giving the specimen the appearance of a single large crystal and making it quite different from most other Biotite specimens. The group has an intense luster, is associated with feldspars, and is in excellent condition.
In addition, this specimen has added historical interest, having been collected at the beginning of the 20th century, as is the case for the great majority of the specimens that formed part of the prestigious Otto Gruson collection.

Geologically, the Biotite crystallized in pegmatites associated with the alkaline igneous rocks of the Ilmen Mountains Complex. These pegmatites are renowned for their exceptional abundance of rare-element and rare-earth minerals, making this locality one of the world's classic and most important mineralogical localities.
Ilmen Mountains, Chelyabinsk Oblast, Ural Federal District  Russia

Specimen size: 6.8 × 6.7 × 6.1 cm = 2.68” × 2.64” × 2.40”

Main crystal size: 6.2 × 5.4 cm = 2.44” × 2.13”