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Collect Rocks Day

Updated on October 7, 2014

Celebrate Collect Rocks Day!

Collecting rocks is a great way to learn about the world we live in. When you do research into what type of rock you have found you can learn how that rock was formed, what geological processes were necessary to create that rock. September 16 is Collect Rocks Day. So, go in search of some rocks and try to identify what you've found.

Rocks fall into three basic categories: sedimentary, igneous, and metamorphic. Sedimentary rocks are formed by sediment deposits becoming compacted and compressed over time. Igneous rocks are rocks formed from volcanic activity. Metamorphic rocks were once either a sedimentary or igneous rock (or sometimes another metamorphic rock) but were exposed to high temperature and pressure for long enough to undergo a chemical change and become an entirely different rock. Some "rocks" you may find might not even be rocks at all but minerals. Minerals are the "building blocks" of rocks and they have definite chemical formulas.

Take a look at my rock collection and read about how these common rocks are formed.


Geodes can be either sedimentary or igneous rocks. They look like dull, ordinary rocks on the outside but when you break them open they have crystals on the inside. They are formed (it is believed) when water works its way into a cavity within a rock and leaves mineral deposits which harden over time forming crystals.

This geode has agate banding, which means it's probably an igneous rock.

Rose Quartz

Quartz is a rock-forming mineral. It is formed from cooling magma that causes silicon and oxygen to combine. Rose quartz is created by titanium impurities in the quartz.


Citrine is another type of quartz. Citrine is quartz that has iron impurities. The color of citrine depends on the level of oxidation in the iron. If the oxidation state of the iron is increased the quartz becomes purple and it's called amethyst.


Bloodstone is a dark green mineral with red flecks. It's a type of chalcedony, which is yet another type of quartz. Chalcedony is a cryptocrystalline quartz, which just means the crystals that form it are so small that it creates a naturally smooth formation. Bloodstone gets its green color from chlorite and the red flecks are due to iron oxide.

You can see the red flecks a lot better in this picture.

Snowflake Obsidian

Obsidian is an igneous rock. It's volcanic glass that is formed when molten lava cools quickly. Snowflake obsidian contains white "flakes." These white inclusions are cristobalite crystals.

Lapis Lazuli

Lapis Lazuli is a blue stone with gold flecks. It is a metamorphic rock. Lapis lazuli is a combination of many minerals. The blue color is due to sulfur, and the gold flecks are the mineral pyrite (also known as Fool's Gold).

You can see the gold flecks a lot better in this picture

Red Tiger's Eye

Tiger's eye is a pseudomorph mineral. It is formed through the process of metamorphism, but it is still a mineral because it changes from one mineral to another mineral. It has been believed that tiger's eye is formed by crocidolite being replaced by quartz. It has a chatoyant luster. Red tiger's eye is created by heat; it can occur naturally but can also be done artificially.

A Rock I Found

The rest of the rocks on this page I actually bought from the Discovery channel store, so I cheated by already knowing what type of rock they are. This rock, however, I actually just happened across while I was walking home one day. I think it's marble (a metamorphic rock), but if anyone knows what type of rock it is feel free to correct me.

Rock Identifying and Collecting Supplies

The necessary tools for rock testing are diluted hydrochloric acid, a streak plate, and a glass plate. Certain rocks react to hydrochloric acid and sometimes using HCL is the only way to differentiate between two similar-looking rocks. A white streak plate will let you know what color streak the rock leaves. A glass streak plate is used to determine the hardness of a rock in the simplest way. Of course, buying a book to let you know what properties certain rocks have will be useful as well.

White Streak Plates - set of 10
White Streak Plates - set of 10

Clear streak plates to help you determine the true color of the rocks you find.

Streak Plates - Glass - 10 Pack
Streak Plates - Glass - 10 Pack

Glass streak plates to help you determine the hardness of rocks you find.

Dr Clark Digestive Power! Hydrochloric Acid (HCL) 5%, 1 oz
Dr Clark Digestive Power! Hydrochloric Acid (HCL) 5%, 1 oz

This is 5% Hydrochloric Acid which should be enough for testing rocks. Always handle HCL with care.

Smithsonian Handbooks: Rocks & Minerals (Smithsonian Handbooks)
Smithsonian Handbooks: Rocks & Minerals (Smithsonian Handbooks)

This is a great book for determining what kind of rock you've found. It has pictures and properties of rocks and minerals.


© 2012 Marigold Tortelli

Do you collect rocks?

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    • John Dyhouse profile image

      John Dyhouse 3 years ago from UK

      I have always been fascinated by geology and have collected rocks and fossils (very small ones) on and off over the years particularly when my sons were young. A very interesting and informative lens.

    • DrBillSmithWriter profile image

      William Leverne Smith 4 years ago from Hollister, MO

      I'm fascinated by the variety... SquidAngel blessed! ;-)

    • tonybonura profile image

      Tony Bonura 5 years ago from Tickfaw, Louisiana

      I collect rocks in order to be prepared for "Throwing Rocks Day!" Get ready, it's coming down soon.


    • artbyrodriguez profile image

      Beverly Rodriguez 5 years ago from Albany New York

      I have a couple of rocks that I have found and kept over the years. I find them very interesting. Nice lens!

    • kimbesa2 profile image

      kimbesa 5 years ago from USA

      I have to resist the temptation now, but if I'm in the right kind of place, like a rocky beach, I just can't help myself...

    • ItayaLightbourne profile image

      Itaya Lightbourne 5 years ago from Topeka, KS

      Yeup! Collect them in nature as well as I buy ones that I'm drawn to at the moment. I love my rocks. :)

    • Country-Sunshine profile image

      Country Sunshine 5 years ago from Texas

      I collected rocks when I was a child, and still have them to this day!

    • FantasticVoyages profile image

      Fantastic Voyages 5 years ago from Texas

      Not into collecting much of anything, but my brother collects all types of rocks and fossils. Informative article... thanks for sharing!

    • poldepc lm profile image

      poldepc lm 5 years ago

      I don't "now"...but have still the collection of my kids in posession

    • profile image

      Terrie_Schultz 5 years ago

      I love rocks! I have lots of beautiful rocks I've collected over the years.