The Magnifying Glass

Eggshell Salt Geodes.

 

One of our geodes when almost dry

 

Dawn recently had a post up about making eggshell geodes with her kiddos, and I just had to laugh as soon as I saw it because my daughter and I had been doing the very same project that very same day.  Apparently Dawn and I are very in-synch when it comes to our kid-science projects!  Anyway, eggshell geodes are a fun and very easy project that you can do fairly last minute, provided that you've got a few eggshells left from baking or breakfast.  Here's how it works:

 

Eggshell Salt Geodes

Materials:

Epsom salt

Hot water

Food coloring

Eggshells

 

Begin by taking eggshells that have been broken at the middle and trimming them slightly with a pair of sharp scissors or a serated knife to get a fairly even edge along the top.

 

 

Arrange your eggshells in an egg carton so that they have a place to sit upright when filled. 

 

Make the salt solution by mixing Epsom salt into hot water until the water cannot hold any more salt.  In other words, you will pour salt into the water (we used about a cup and a half of water, but you could easily get by with much less), mixing well with a whisk until you see that the salt is no longer able to dissolve into the water and a slurry begins to form.  At this point, you can add a bit of food coloring as well.

 

 

Fill the eggshells with the salt solution.  You can then set them aside to dry.  This will take some number of days, depending on the humidity level in your house.  As they dry, salt crystals will begin to form inside the shells, giving them an appearance similar to a geode.  As an alternative, you can also put the eggshells into the refrigerator for a few hours and from what I hear, crystals will form this way as well.  Nearly instant gratification! We haven't tried this method at our house yet, but I'm pretty sure that it is what Dawn did with hers, and they seemed to have turned out well. 

 

one of Dawn's geodes

 

For more about eggshell geodes, and geodes themselves, you can take a peek at Dawn's post here.

 

--- Annie

A Nature Exchange Book List.

All of us here at TMG are very excited to have so many families signing up for the nature exchange!  It should be really fun and interesting, and I thought that I might share a few useful books to help you get started finding and identifying some of the natural treasures in your neck of the woods.  Here are a few favorite titles that you might find helpful!

 

Out of the Ocean by Debra Frasier

 

 

The Tree Book by Gina Ingoglia

 

 

My First Pocket Guide to Rocks and Minerals by National Geographic

 

 

My First Pocket Guide to Wildflowers by National Geographic

 

These are just a few titles among many that could be great resources for the exchange.  Does your family have any favorites you'd like to share? 

 

--- Annie

Petoskey stone

If you’re from Michigan, or have ever visited Michigan, you probably know all about petoskey stone.  After all, it is the “state stone” of Michigan.

But I’m not from Michigan, and so my husband had to educate me; allow me to share the story with you.

When taking a stroll along a Lake Michigan beach in northwestern Michigan (on the lower peninsula), keep your eye out for promising pieces of limestone. Pick a stone and wet it a little—if you’re lucky, a web of crooked and variously-sized hexagons will appear in the stone right before your eyes.

 Wet petoskey stone.

It can be nearly impossible to tell regular limestone apart from a petoskey stone unless the stone is wet.  In fact, collectors often carry a small container of water with them as they look for the stones so they can tell on the spot if they’ve found what they were looking for.  (Other collectors prefer to go out in a light rain so they can more easily find these special stones.)

 

When a petoskey stone is dry, it can be hard to tell it apart from ordinary limestone. 

 

The stones get their name from the resort town of Petoskey, Michigan, where they were (and still are) sold to tourists as souvenirs.

Petoskey stone is technically limestone, but can you guess how the distinctive hexagon shapes came to be? If you guessed that they are fossilized coral, then you are right. (The stone in the first photo is a little unusual in that you can see the ridges of the sides of the coral running down the sides of the rock, in addition to the distinctive coral shape at the top that is the hallmark of a petoskey stone.)

Coral, of course, favors warm salt water, and Lake Michigan is a fresh water lake that isn’t particularly warm most of the time. So how did fossilized coral end up in Michigan?  Well, scientists believe that a very, very long time ago, the land now known as Michigan was near the equator.  Not only was it warmer, but it was covered by a huge shallow sea.

Over time, the land mass broke apart and our modern continents began to take their shape.  The land under the shallow sea was lifted up a bit and the shallow sea dried up.  As the land mass of modern Michigan shifted northward, the climate also became too cold to support tropical sea life such as a coral reef.

You may then wonder how the coral became embedded in rock.  The coral was likely buried in mud filled with lime (calcium carbonate) that was covered by more and more mud over time. As the water was squeezed out, the intense pressure hardened the mud and coral into stone.

Petoskey stones can be highly prized and are often polished to bring out the beauty of the coral.

Here’s a link that gives the history of petoskey stones and provides guidance for hand polishing any treasures you may find on the shores of Lake Michigan.

Be sure and share your rock hunting stories with us here at TMG, and photos of special rocks you find on the TMG flickr pool.

Wishing you happy rock hunting,

~ Nancy

A bit of fossil hunting.

There are many ways to hunt for fossils, so I won't even begin to try to cover that topic in depth; instead, I thought I'd share some inspiring photos and a few tips from a recent day-trip 'expedition' we took as a family.

 A view of Maryland's Calvert Cliffs along the Chesapeake Bay, a popular fossil-hunting site.

 

 
My mom, holding a large chunk of rock that we found just sitting on the sand; we put it right back.

Fossils are plant or animal specimens (or traces of them, such as footprints) that have been preserved in rock.  Often, fossils are found in sedimentary rocks, which are formed when layer upon layer of silt and minerals from a body of water are deposited, dried, and compressed into layers. 

Plants and animals caught in the layers are preserved for many, many years until at some point, they become exposed again--typically--via natural erosion and human excavation.  

 
Here's a closeup of the base of a cliff at Calvert Cliffs State Park.  Excavating at the base of a cliff is a big no-no, because it can undermine the cliff and create a dangerous landslide.  But you can (cautiously) look.

Fossil hunting is not without controversy, and it's a great way to open up a discussion with kids about the importance of protecting natural resources for future generations.  Fossil collecting should only be done in accordance with local law (it's illegal to possess any fossils at all in some countries).  Also, to be fair, rare fossils should be shared with everyone.  Local museums are a great place to donate special finds.

My daughter, pointing out some fossilized shells in a hunk of rock that had fallen from the cliff onto the beach.

 

Publicizing locations for finding fossils is also controversial, because some people do try to scavenge as many as they can and sell them for profit.  In the process, they can do great damage to the fossils and the landscape, preventing the public at large from enjoying these treasures. 

However, around the world, there are still quite a few publicly-accessible locations where fossil hunting is easy, and allowed.

My dad, holding a bit of rock we found at the same beach.  I made sure to take clear photos so we can try to find out more about the fossils we saw and perhaps report back here.

If you have no idea where to find fossils in the area where you live, and you are in the U.S., a great place to start is your state's geological survey or geological society.  They often publish guides or other tips for local fossil hunting, such as this one for Minnesota,  this one for Pennsylvania, or this one for Maryland. I also found this link to a long list of surveys, including some for countries around the world.  Here's a fossil-hunting page from the British geological survey, for example. 

Of course, a straight Internet search is a quick and easy way to find local fossil hunting grounds.  (Here's a page for a fossil-hunting site in Nova Scotia, and here's one for Sicily.)  There are also various websites and books that collect, with great specificity, fossil hunting sites for entire counties, regions, or countries; poke around and they pop up easily enough.  

  
 At Calvert Cliffs, the fossils we saw seemed to be in two very different kinds of rock.

Creek banks, dry river beds, and exposed cliffs are all good places to start looking for fossils.  Sedimentary rock is typically formed from mineral deposits left behind by ancient seas and waterways, and modern waters erode through the layers of ancient rock to expose fossils.  Quarries, or even roadside ditches, dug by human beings, can also be rich sources of fossils.
 

My son and his fossil find.  We left this fossil for others to enjoy.

 

For kids, it's rather exciting to visit a place where fossils are immediately visible, sticking straight out of the rock.  With a little research, you can find such a place within driving distance to share with them; or short of that, there are many small museums that have fascinating fossil treasures to share with everyone.

Have you ever been lucky enough to find a fossil?

--Nancy