The chunk of rock sitting on this suburban street corner is an interesting piece of geological material.
"Unique to Vancouver Island is the jasper form known as Dallasite, named after the road near Victoria where it was discovered, at the south end of Vancouver Island. It is officially recognized as the third most important gemstone in British Columbia.
Dallasite is a fantastic and jaw-dropping artistic display of green, black and white colours, but it often includes blue, yellow, red and all the colours on the spectrum. Dallasite is a jasper breccia made up of quartz, altered basalt, epidote and pumpelleyite. It is thought to have been formed as pillow lava underwater.
Each piece paints a picture in beautiful blocky artwork. No two stones are alike. Many even come with mossy black agate spots in the creamy seams. Some have blue tinges in the quartz and others tinge yellow.
As a breccia, Dallasite comes in many forms but all share a distinct look. It often has green zig-zags in lightning streaks or displays black dots lining a white background. Dallasite truly reflects the colours of the Pacific Northwest." (Courtesy: British Columbia Rockhound website)
Dallasite can be found most anywhere on Vancouver Island, whether it is a small rock on the beach or a large boulder exposed by erosion or landslide. Next time you are at the beach, take a look among the rocks and pebbles beneath your feet. Studying this sample should assist you in recognizing even the smallest pieces of Dallasite.
Belonging to the mineral family of quartz, dallasite is a cryptocrystalline form of silica that is both hard and semi-transparent. As a member of the quartz family, Dallasite is composed of silicon dioxide, or SiO2, which is a common chemical compound found in many minerals. Its cryptocrystalline structure gives it a unique appearance and texture, but it shares many characteristics with other types of quartz. Dallasite is a jasper breccia made up of quartz, altered basalt, epidote, and pumpellyite. It is thought to have been formed as pillow lava underwater. Its color varies depending on its source and how it has been cut and polished, ranging from gray, and white, to black with a mottled appearance. It has a hardness of 6.5 to 7 on the Mohs scale, making it relatively hard, but not as hard as some other common gemstones like diamonds.
In order for you to log this EarthCache you must answer the following questions (please DO NOT post your answers in your "found" log, but rather send them to me via messaging or email):
- Besides the white veining and gray facings, what other colours can you see on the boulder?
- Describe the direction of the veining in the boulder (for example, horizontal, vertical, angled to the left, to the right, etc.)
- Who is responsible for this boulder being here?