While walking around Geocaching HQ, I noticed a really cool mosaic in the ground. It incorporates the geology in a similar way that the Hollywood Walk of Fame does. The mosaic is made of terrazzo, which is a composite of different types of materials including glass, marble, quartz, and other natural crystals. Terrazzo is held together by epoxy before it is set. The name "terrazzo" comes from the Italian word for terrace, reflecting its historical use in Venetian construction.
When walking by on a sunny day, the mosaic will shine in luster due to the numerous cleavage planes within the grains. Cleavage is the tendency for a mineral to break a predictable way due to weaknesses in the molecular crystal structure. Cleavage planes are always reflective and are easy to detect because by their smooth surfaces. Note that in the image below, cleavage planes 1 and 2 are much smoother than the fracture surface plane, which is rough and bumpy.
Works Cited
https://www.geocaching.com/geocache/GCAH824_hollywood-walk-of-fame
https://sternberg.fhsu.edu/research-collections/geology/mineral-classification-page.html
https://opentextbc.ca/physicalgeology2ed/chapter/2-6-mineral-properties/
https://openeducationalberta.ca/practicalgeology/chapter/2-3-mineral-properties/
TO LOG A FIND ON THIS CACHE YOU MUST ANSWER ALL THE QUESTIONS BELOW. YOU CAN CONTACT ME THROUGH MY EMAIL OR THE GEOCACHING MESSAGE CENTER TO SEND YOUR ANSWERS. ANY INCORRECT ANSWERS MAY RESULT IN A CLARIFICATION RESPONSE FROM ME.
1. "Lake Union Center" on the first line of your email AND list all geocaching names of your party so I can match your answers to them. If you all want to learn something, I would prefer each cacher send me individual emails in the spirt of earthcaching.
2. Take a close-up photo of the terrazzo using some sort of scale. Geologists often use coins, GPS', pens, shoes, notebooks, ect. You might want to be creative in what you use for your scale, however, the scale that you choose is entirely up to you. Make sure your photo is close enough to capture the mineral grains which should be clearly seen. This photo MUST be attached to your "found it" log. Please do not send any photos through the message center as Groundspeak compresses images. Each log MUST have a unique and different photo. No two logs may contain the same photo.
3. Describe the (a) colors, (b) average grain sizes, and (c) textures of the terrazzo at this location. Are all the grains more or less the same size or do they vary greatly?
4. Describe the mineral cleavage using the charts above. Tell me if the cleavage is either (a) good or poor, (b) the number of cleavage planes that are visable, and (c) the angle these planes make with each other. Hint: (a) and (b) are based on the reflectivness of the grains when viewed from different angles (i.e. from the top vs the side) and (c) is read directly from the chart in the cache page based on your answers to (a) and (b).
5. Are these grains aligned in an orderly fashion or are they all randomly distributed? What does this tell you about the strength of the material?