There is a circular array of granite boulders around the base of a piece of art in front of the BCIT Marine Campus building. This would be an average granitic array, except for the one boulder on the very west side of the art. This boulder has something very unusual – a large lighter spot facing the west. This spot is almost entirely composed of feldspar, a very common rock forming mineral. Feldspar does not usually appear in this size. The common salt and pepper of granite is often hornblende (pepper) and feldspar (salt).
Feldspar is the most abundant mineral in the world’s crust.
Feldspar is a generic term for several minerals, the two main ones are orthoclase (k-spar) and plagioclase (na-spar). They are both light colored to white and are not easy to tell apart. The way to tell is plagioclase has striated (little lines across the face) crystals and orthoclase does not.
If you look at the white feldspar area closely the glassy spots you see are quartz, the shiny black spots are biotite mica the shiny white spots are muscovite mica.
Feldspar is commonly mined for making glass and ceramics and China and Turkey are presently the main world producers. The largest mine in the world was in North Dakota but it is now closed. The cleaner, Bon Ami uses feldspar as an abrasive in its cleaners.
Your task to log this earthcache is to send me an email or message me the answers to the following questions.
What size is the white spot in feet (or meters). It is roughly rectangular.
Tell me the type of feldspar it is by looking for the plagioclase striations or the orthoclase non striations.
Send your answers at the same time as logging. Logs with no answers will be deleted.