Yes, rocks do tell stories! Earth is made of rock. Thousands of different types of rocks and minerals have been found on Earth. Most rocks at the surface (where humans can see) are formed from only eight elements (oxygen, silicon, aluminum, iron, magnesium, calcium, potassium, and sodium), and these elements are combined in a variety of ways to form very different rocks. Each rock tells its own story, and those stories in combination record the history of Earth.

Earth's surface is constantly changing: mountains are built, rivers cut canyons, wind and water carry rock and deposit it in new locations, flat layers became folded and faulted, and hot, molten rock from below Earth's surface seeps out as lava. Earth is over 4.5 billion years old, and most of that history has been destroyed by erosion, burial, and modification from heat and compression at depth. However, some fragments remain, like the Acasta gneiss from Canada (dated to about 4 billion years, this is the oldest known rock on Earth) and the Jack Hills zircon from Australia (dated to 4.4 billion years old, these are the oldest known minerals on Earth). By studying how rocks form and how they become new rocks, scientists have developed a good understanding of how Earth formed and how it has changed through time.

Since Earth is made up of rock, no one "discovered" a first rock. In fact, it is challenging to know who the first person to think critically about rocks might have been. Like all science, the study of Earth has evolved with technology and human understanding. Generally, the first advanced thoughts around Earth (including mineralogy, cartography, geography, and geology) are attributed to ancient Greece. The oldest known maps are preserved on 2300 B.C. Babylonian clay tablets. Xanthus of Lydia (modern day Turkey) and Herodotus of ancient Greece were historians who occasionally wrote about geology and the natural world during the 5th century B.C. (500-400 B.C.).

The concept of a spherical Earth was widely accepted in Greece around 350 B.C.. Strabos of Greece wrote a book titled, "Geography" before 24 A.D. Pliny the Elder of Rome wrote one of the earliest encyclopedic works on natural and geographic phenomena shortly before his death in 79 A.D. Modern geology is attributed to James Hutton from Edinburgh, who dedicated himself to the study of rocks beginning in 1768. He laid the foundation for scientific geology.

There are many various types of rocks and many can tell fascinating stories about the way they formed. Some rocks will only have minerals that can form at very high pressures, so we know that the rock needed to form deep in the earth or in a place where an asteroid struck. Some rocks have fossils in covered in mudstone, rock which formed from mud under the pressure of rocks above it. Those can tell us stories about the place where the animal died.

People have known and used rocks for a long time, even before people called themselves scientists. One of the first minerals that was discovered a bit more recently was magnetite, a magnetic mineral that was used for the first compasses. We do not know the exact person that discovered the mineral, but many ancient civilizations knew about it and used it to navigate in the ocean.

Rocks contain information about how the rock was formed, and what forces the rock was subjected to before we found it. By looking at many rocks, we can construct a story about the history of the earth.

Our ancestors have known about rocks since long before our ancestors were human beings. Ancient peoples certainly knew that different kinds of rocks were useful for different things, such as different building materials, or containing different kinds of ores for smelting. The first person credited for looking at rocks as records of the past is often Leonardo da Vinci, but even he probably wasn't the first (he was also largely ignored).

Rocks tell lots of stories. They tell whether they formed from sediments that got pressed together under water, or from volcanic eruptions. Some of them tell about ancient plants and animals that lived when the rocks were being formed. Scientists can tell how old the rocks are, because the rocks have different ratios of isotopes of elements such as oxygen, depending on when they were formed.

What do you think about scientists and rocks? When do you think rocks were first discovered? How old do you think you were when you first discovered a rock?