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Roger Weller, geology instructor

rock collection
by Rachel Norton
Physical Geology
Spring 2017

                               Categorizing My Daughter's "Pretty Rocks"

     As a child going for walks with my mother, it never failed that she would come back with at least one “pretty” rock that she found on the ground.  She would point out the different colors in the rock, or the shape, whatever she thought was pretty about it.  Even as a child I could appreciate the rock, but I didn’t get it, it was a rock, literally hundreds of them on the ground that looked just like the rock she had picked up.  She would take them home and leave them on the back porch and after a while they would just get thrown into the backyard to blend in with the rest of the desert landscape.

My mom’s current collection, photo courtesy of R. Norton

     Fast forward and now I’m a mother taking a walk with my daughter who had just learned to walk.  She was no more than a year old trying out her first pair of real shoes in the backyard.  She walked around for a minute enjoying her freedom when she suddenly stopped, bent over and picked up a rock.  She looked it over smiling then walked over to me and gave it to me and said, “Pretty”.  

     My mom still goes on walks and collects her pretty rocks.  My daughter has also started her own collection of rocks.  While my mom picks rocks based mostly on their color composition, my daughter goes for shapes.  She uses her imagination to see them as other things.  Her favorite rock is a flat, round, brown rock with a chip in it.  To her it looks like a cookie.

     But why do they collect rocks?  Is it genetic?  If it is genetic, the gene skipped me and my sister.  I have a younger daughter who also collects rocks, but I think she is doing it just because her big sister, who she worships, does it.

     What does it mean to collect?   When people think of collecting, they may imagine expensive works of art or historical artifacts that are later sold to a museum or listed on eBay. The truth is, for many people who amass collections, the value of their collections are not monetary but emotional —and often, not for sale. Collections allow people to relive their childhoods, to connect themselves to a period in history or to a time they feel strongly about. Their collections may help them to ease insecurity and anxiety about losing a part of themselves, and to keep the past present.  Some collect for the thrill of the hunt.  Collecting may provide psychological security by filling a part of the self-one feels is missing or is void of meaning. When one collects, one experiments with arranging, organizing, and presenting a part of the world which may serve to provide a safety zone, a place of refuge where fears are calmed and insecurity is managed.  Motives are not mutually exclusive; rather, different motives combine in each collector for a multitude of reasons. #1

     According to Mark B. McKinley, Ed.D., “For some people collecting is a quest, in some cases a life-long pursuit that is never complete.”#2  I feel that this quote truly sums up my mom and daughter.  Their eyes are constantly on the ground looking for the next great “pretty”.

     I’m pretty sure that this is a safe hobby.  I don’t see her using these to calm any fears or insecurities at this age.   I also don’t see any harm with the handful of rocks that are brought into my house almost every day that end up taking a bath with her so that she can see their true color and shape.  The majority of them end up back outside.  Some thrown back on the ground, some that have been deemed acceptable by her end up on our fence, the ones that are just a tad bit more special end up in her special box, and the most precious ones are kept in her room…out of her sister’s reach.

     I thought it would be a fun project to get some of my daughter’s favorites and identify exactly which types of rocks these actually are.  My hope is to peak her interest even further in these rocks and not just see them as pretty shapes.

     With her help, we picked out 3 rocks that she wanted to have identified so that she could learn more about them.

     The first rock is the newest to the group; she calls it her “Ship” rock.  She is really into watching a show on TV right now that from time to time has a boat on it so when she is playing reenacting this show, she brings this rock out.

“Ship” rock, courtesy of R. Norton

     “Ship” rock is actually a piece of quartz.  Quartz is a mineral composed of silicon and oxygen atoms in a continuous tetrahedral framework.  Quartz is the second most abundant mineral in Earth’s continental crust, behind feldspar. #3

     After explaining to my daughter the type of rock it was, where it came from, and how it was made, the thing she thought was most fascinating about this rock was how the cracks (see picture above) were most likely formed from earthquakes.  She’s only 5 and has lived in Sierra Vista her whole life and didn’t know that an earthquake was so it was fun to then switch gears and teach her a little bit about earthquakes.

     The next rock we identified is called the “hot dog” rock because she thinks it’s shaped like a hot dog.  This rock is quite interesting because it is a siltstone on one side and sandstone on the other (pictures below).  Siltstone is a sedimentary rock composed mainly of silt-sized particles.  It forms where water, wind, or ice deposit silt, and the silt is then compacted and cemented into a rock. #4  My daughter was having a blast letting her imagination run wild as to how this rock was formed.  Was it pressure from the weight of being underground?  Was it cemented together and if so, with what?

Siltstone side of the “Hot Dog” rock, photo courtesy of R. Norton

Sandstone side of the “Hot Dog” rock, photo courtesy of R. Norton

     I saved the best for last with her.  It was her “Cookie” rock.  It is the rock she has had the longest (3 yrs) and is by far her favorite.  I knew right away what type of rock it was, but I wanted to see if she could figure it out.  After looking at it for a minute and comparing it to her “Hot Dog” rock, she figured out all on her own that it was sandstone.  

     Sandstone is a sedimentary rock composed mostly of quartz sand, but it can also contain significant amount of feldspar, and sometimes silt and clay.  Sandstone that contains more that 90% quartz is called quartzose sandstone.  When the sandstone contains more than 25% feldspar, it is called arkose.  When there is a significant amount of clay or silt, geologists refer to the rock as argillaceous sandstone.  The color of sandstone varies, depending on its composition.  Argillaceous sandstones are often gray to blue.  Because it is composed of light colored minerals, sandstones is typically light tan in color.  Other elements, however, create colors in sandstone.  The most common sandstones have various shades of red, caused by iron oxide.  In some instances, there is a purple hue caused by manganese. #5

“Cookie” rock, courtesy of R. Norton

     Once we were done with these rocks, she wanted to go through more of her rocks.  We were able to identify most of them as sandstone or quartz.  She was so proud of herself.  Her Kindergarten teacher told me the next day after school how she had told them all about how she learned what types of rocks her favorite rocks were.

     I believe I accomplished my goal of getting her interested in her rocks for more than just the shape of them and I think she sees them more than just pretty.   

The pretty rock collector herself, photo courtesy of R. Norton


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