What kind of rock is this? Find out at the Gem & Mineral Show
Sep 11, 2024 12:44PM ● By Raechel Kolb
I ran as fast as my 10-year-old legs could carry me, clutching an enormous rock in both hands.
“Grandma, what kind of rock is this?” I held the beautiful white stone out proudly so she could inspect it with her wise eyes.
The waves lapped gently against the smooth rocks lining the shore of Huron Bay, where my family spent summers. A warm breeze lifted my grandmothers gray hair from her face. I loved that shore, and her and the rock in my hands.
Bending down, Grandma took the rock from me, and turned it over in her hands. Then she announced her verdict: “This is a puddingstone. It was carried here by a glacier. See those red rocks that look like raisins? Those are called Jasper. I’ll put this in my rock garden so you can see it whenever you visit.”
You May Also Like: Rockhounding: A hobby that’s good for your health
I studied the small red stones embedded in the big white rock. Just then, my sister came running with her own rock, calling out her question. I waited eagerly, knowing my rock would be in Grandma’s garden and hoping my sister’s find was just as special.
Decades later, I returned to that shore and borrowed my uncle’s rowboat. My husband and son joined me as we rowed across the bay to a shoal. On the shore, we tied the boat to a nearby tree stump. We wandered along the shore, beachcombing as we went.
Within minutes, my 12-year-old son came running to me, holding a bright white rock out for me to inspect.
“Mom, what kind of rock is this?”
“That,” I replied, “is a puddingstone.” I pointed out the Jasper embedded in the white matrix, just as my grandmother had done.
My husband, a geologist, chimed in, explaining how glaciers had advanced, carving out the Great Lakes and carrying boulders from Canada. With crushing weight, these giant ice-fields flattened hills, demolished forests and carved U-shaped valleys. When the glaciers retreated, they left behind moraines, erratic boulders and the questions that have fascinated humanity for millennia: “What kind of rock is this, and how did it come to be here?”
It occurred to me then that the question is universal, rooted in human curiosity. It has led to the discovery of fossils, gems, metals, caves and geological wonders across the earth.
You May Also Like: How to start a rock collection
Humankind has brought rocks back from mountains, caves, islands, oceans, shores, the moon and even Mars. As we explore our world and others, this question echoes through eons, through generations and wherever rocks can be found.
Geologists, mineralogists and gemologists, along with engineers and scientists, have developed tables, charts and chemical tests to answer this question. Yet, some rocks remain enigmatic, sitting for eons in solid repose. They support the plants and animals, the oceans and islands. Sometimes, they’re buried under miles of other rocks and sediments until churned to the surface by tectonic movements or erosional forces.
And then, some human hand picks them up and wonders, “What kind of rock is this?”
