August 26, 2002
In the area where I live in Vancouver, British Columbia, interesting looking rocks and stones from a nearby river valley are sometimes used for decorative purposes. The one pictured above is about 3" x 5" (7.5 cm x 12 cm) and looks a bit like the Chinese yin-yang symbol. It's likely an inclusion of a biotite-rich metamorphic rock in granite or a similar type rock - biotite is typically found in light colored igneous rocks such as granite. The smooth somewhat flattened shape of this stone is characteristic of rocks that have spent much of their existence in rivers or streams.