Alongside the hiking path or the stream bed, we regularly pass by stones that hold interesting rock compositions or secret minerals. In honor of International Rock Day this Saturday, stop and take a closer look at some of these rocks. Their details may reveal what they are made of and how they came to be. You might even find something rare or beautiful! Exploring rocks can spark a whole new world for children to explore. Listen to the Rockhounds: Geology Rocks!
Where to Find Cool Rocks:
Good places to find interesting rocks are near or below rocky outcroppings such as you might find when hiking. Pieces of rock will fall from higher peaks, exposing new rock from underneath. Dry washes or arroyos are filled with rocks of various sizes and makeup, sometimes revealing spectacular finds.
Construction sites may either turn over the ground exposing new rocks or deposit new rocks fresh from a far-away quarry. While we don’t recommend ever entering a construction site, you might look near the outside of an inactive site or downhill from a recently completed project.
Beaches will often reveal rocks, minerals or fossils that have been washed up by the tide. Sometimes softer rocks are deposited alongside rivers and streams. Wearing sturdy footwear, you can walk along the edge seeking treasure. Because Southern California deserts were once underwater, there are fossils still to be found in our nearby desert areas.
Types of Rock & Where They Came From:
There are three main types of rock that can be found. Igneous Rock is pushed forward from the earth during volcanos and lava flow. Obsidian, basalt and granite are examples. Igneous rocks are typically darker and / or heavier than other types of rock, and fine-grained with interlocking grains of different colors are often visible. They may contain small hole or voids within them as well. Sedimentary Rock is formed by the compacting of sediments, minerals and plant or animal debris such as fossils. Sandstone and limestone are common examples, and you might recognize sedimentary rock as being light in color and / or weight. Occasionally fossils are visible within them. Metamorphic Rock is rock which have changed in formation because of heat or pressure. They often come from deep within the ground. Examples include soapstone, marble and gneiss. You may notice layers or striations of darker and lighter shades, and metamorphic rocks typically have a crystalline texture. Once you become familiar with the look of the different types of rocks, you’ll more easily be able to identify rocks you aren’t yet familiar with.
What to do When You Find Something Interesting:
In short, identify it, admire it, and leave it behind for someone else to enjoy! Sometimes you might find a small stone that is especially pretty that you want to keep. If you are not in a public (state or national) park, some else’s private property, or another protected location, taking a few small rocks is probably OK. You don’t want to teach children to collect more than they can appreciate, though.
Rock tumbling is a way of smoothing and polishing stones using a rock tumbler with grit or pellets inside.Small rock tumblers can be purchased commercially.
If you find your child has a love for rocks, minerals and gems, you might want to check out a local rockhounding group. The Pasadena Lapidary Society holds workshops on the second Saturday of each month in Arcadia.
| Types of Rock You Might Find in Southern California Include: | |
| Agate | is commonly found throughout Southern California. It’s a metamorphic rock made up of quartz or chalcedony. In comes in a wide variety of colors, and often contains interesting patterns. |
| Benitoite | the California State Gem - is a rare mineral that sparkles brightly. When found, it’s most commonly brilliant blue, but can also be pale pink or colorless. Benitoite is often mistaken for sapphire but is much softer. |
| Calcite | is a sedimentary rock that is often present in limestone. It is typically clear or white and is easily recognized it its crystal form. |
| Chert | is a general term for hard sedimentary rocks that include jasper, chalcedony, agate, limestone and flint. It is a mineral of biological origin, often coming from former ocean life or shells. Chert is abrasive and contains silica, and was used historically in the making of weapons such as spears. |
| Garnet | A metamorphic rock and semi-precious mineral. Most often recognized in its translucent deep red color, garnets can actually range the rainbow of colors. Southern California was historically a great source of garnets for use either in jewelry or industrial applications. |
| Gneiss | Is a very common metamorphic rock similar to granite, but harder, and has a particularly high melting point.It is medium- or course-grained, often contains quartz, and is recognized by its bands of irregular coloring often of white, gray, black, pink and / or red. |
| Gold | The California State Mineral- a rare and durable mineral, crystallized gold is not found in significant amounts in very many places, but California is one of them. Gold is most frequently found as a vein running through quartz or (as most fourth-graders in California can tell you) in stream sediment. |
| Granite | is an igneous, course-grained rock made up mostly of quartz. Granite is the most common igneous rock found on the surface level. |
| Gypsum | is a sedimentary rock characterized as a soft, white or gray crystal. Industrially, it may be used to make drywall, plaster, or fertilizer |
| Howlite | is a sedimentary mineral, usually white or gray and white and in its original form looks like a big, hard cauliflower. Howlite can be dyed to mimic other stones, such as turquoise, in jewelry-making. |
| Jade, Nephrite & Jadeite | are very rare but significant deposits can sometimes be found in California. A metamorphic rock, nephrite and jadeite are both types of jade, and are extremely durable. It is most commonly green but can also be a variety of other colors. |
| Jasper | Hard fine-grained and opaque, jasper is a type of chert made up of a mixture of quartz and other inclusions. It is a sedimentary rock most often found in a hue of red or brown, though may also come in other colors. When jasper contains a beautiful pattern it can be polished as a semi-precious stone |
| Limestone | Is a sedimentary rock made up of calcium carbonate. It has a heavy fossil content and may even contain visible fossils. Ubiquitous throughout the Americas, limestone is very soft and light colored, often white, gray or beige. |
| Pyrite | A mineral of lusterous, yellow-brown, pyrite is commonly known as Fool’s Gold. It is a common mineral that can be found almost anywhere, and is special because it may cause sparks when struck with another stone. |
| Quartz & Quartzite | Is a metamorphic rock formed from sandstone. Usually white or gray, it may have a reddish tinge and is characterized by the extremely strong bonds between the grains. |
| Sandstone | is a common sedimentary rock often seen on coastal cliffs. It is relatively soft and made up of sand-sized silicate mineral grains, and often looks a lot like a heap of sand. |
| Serpentinite | The California State Rock is a metamorphic rock mostly composed minerals that gives serpentinite a variegated green hue. Because Serpentine is made up of tiny sheets of silica loosely bonded together is often takes on a scaly appearance and slippery feel. |
| Spodumene | is a common colorless or yellowy dull igneous or metamorphic rock, that is a good source of lithium. When a lustrous, translucent form of spodumene is found it is highly valued as a gemstone. A pink or violet version of spodumene is known as Kunzite. |
| Soapstone | Soapstone typically displays a subdued tone of gray, possibly with a blueish or greenish tinge. It commonly features white veins and occasional swirls of white or quartz, and the high talc content in soapstone gives it a smooth texture and a waxy, soapy sensation on the surface. Compared to granite or quartz, soapstone is softer and can be easily scratched with a fingernail. |
| Tourmaline | Tourmaline, a crystalline silicate with a diverse array of minerals, exhibits a vibrant range of colors including pink and green. While it commonly occurs as an accessory mineral in igneous and metamorphic rocks, its durability allows it to persist through transportation processes such as stream and beach erosion, ultimately becoming part of sedimentary deposits or in sedimentary rocks. |
