Doesn't everyone love geodes? It's peculiar there aren't more books devoted to them. The Cross and Zeitner volume (below) is full of interesting information and beautiful photos; from there you pretty much have to go back to the 1908 Bassler volume. Of course general books on rocks contain information on geodes as well.
This beautifully shaped quartz geode is full of tiny crystals. The highly polished back is equally beautiful. Somehow Gary managed to grind the outer material down to a perfect, thin strong shell without breaking through into the crystals, thus the pendant is very light. The neutral shades will complement any outfit. Won't you order it today?