Two large crystals of kurnakovite, a magnesium rich borate, are emplaced on matrix. The "smaller" crystal, 12 cm across, is doubly terminated, lustrous and translucent, with a light gray color. It is HUGE for the species, in amazingly good condition, and frankly just off the charts compared to what you can normally get in this material. An old piece, collected in 1976 and bought from a rock shop in the Trona area. I have not personally seen comparable for sale in this size range - ever.