Welcome to El Dorado trail! Today is a good day to look at some rocks and some rock formations. Walking along this trail you can encounter some fascinating and interesting features. You can see striations and layers, various types of boulders and stones, some quartz formations. You may see fractures and evidence of fault activity. You can see the distinctive reds of clay soil in between the vibrant greens of mossy growth. It really is a fascinating place to walk and take in the sights of nature.
For today, you will be making one stop looking at some layers of rocks. This “rock face” is popping out of the side of the trail. This rock face spans a good swath of this part of the trail, for the formations to be discussed can be seen in multiple sections throughout the rock face. So wander around, look at multiple sections of the rock, and enjoy the view.
LET’S TALK ABOUT IRON:
Ore is a kind of mineral that contains other, more valuable minerals. Metals are some of the most important minerals found in ore. Deposits of ore are located in many areas around the world, but ore is never found in a pure state. It is always mixed with rocks and other minerals in Earth’s crust.
There are hundreds of different minerals on Earth, but only about 100 are ore minerals. Iron ore is incredibly common and iron is found in several different ore minerals: hematite, magnetite, limonite, and siderite. Hematite in rocks tends to have reddish-brown streaking. Magnetite is darker brown or black streaking. Limonite is lighter yellowish to reddish-orange streaking. And siderite has the lightest streaks typically closer to white.
Iron ore is the source of primary iron for the world's iron and steel industries. It is therefore essential for the production of steel, which in turn is essential to maintain a strong industrial base. Almost all (98%) iron ore is used in steelmaking. Iron ore is mined in about 50 countries. Banded iron formations are worldwide layered sedimentary deposits rich in iron that range in age from 1.5 to 3.8 billion years old, the age of the earliest known rocks. They contain 30–60% Fe3+. No molecular oxygen was present in the earth's atmosphere until 1.5–2.0 billion years ago. Most deposits of iron ore in the world are found in rocks known as banded iron formations (BIFs).
Extracting, or removing, metal from ore requires several steps. First, the ore and its surrounding material are mined, or taken from the ground. Second, unwanted rocks and minerals are separated from the ore. The rock mixture may be crushed, washed, and filtered to obtain pure ore. Magnets, electricity, or other technologies also may be used to purify the ore. Third, the ore is treated with heat, electricity, or chemicals to extract the metal. Smelting is the oldest way of extracting metal from ore. In smelting, ore is heated until liquid metal flows out. Last, the extracted metal may be refined, or purified. It also may be combined with another substance to create an alloy. Iron ore is a mineral substance which, when heated in the presence of a reductant, will yield metallic iron (Fe). It almost always consists of iron oxides, the primary forms of which are magnetite (Fe3O4) and hematite (Fe2O3).
SO THE TASK:
Look at the rocks, look for splotches and swaths of reddish-brown or orangish color (rust color) rocks. Thes are areas when you see the iron presence in the rock, taking on that rusted hue having been exposed to the oxidation effects of oxygen, water, air, and time. Oxidation is a type of chemical weathering where a substance or object reacts with oxygen. You will answer the following questions regarding Iron as you can observe in this rock face and from the information provided.
QUESTIONS:
- How many are in your group and their caching names (only need one set of answers).
- Looking at the area, find some of those rust-colored areas you think could be the evidence of iron. Describe the color of the area you are observing and the surrounding rock.
- Based on the color you have observed, do you believe this is most likely hematite, magnetite, limonite, or siderite?
- I am a process that occurs on rocks because of the presence of iron in them. I result in the formation of rust that gets removed from the rocks easily. What am I?
- The rust formed in rocks loosens the original structure of the rock making it weak, so the rock gets broken and/or is subject to breaking and fracturing. Can you see evidence of fracturing or brittleness in the rocks? Describe the texture along an identified fracture.
- Near and around this rocky area you should also see some exposed clay soil areas. Compare the color of the iron deposits on the rocks to the color of the clay soil. What can you conclude about the clay soil through this comparison.
- OPTIONAL: Take a picture at the site (selfie or group) or take a pic of GPS or your Geoname written on a paper next to the rock/iron observation.
SOURCES:
Science Teacher/Co-Worker: Personal Source of info, help me identify rock features and steered me towards iron deposits, as well as directed me to focus on the clay in the area as well.
SCIENCE DIRECT: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/banded-iron-formation#:~:text=Banded%20iron%20formations%20are%20worldwide,1.5%E2%80%932.0%20billion%20years%20ago
GEOSCIENCE AUSTRALIA: https://www.ga.gov.au/education/minerals-energy/australian-mineral-facts/iron#:~:text=Most%20deposits%20of%20iron%20ore,formed%20millions%20of%20years%20ago
USGS – SCIENCE FOR A CHANGING WORLD: https://www.usgs.gov/centers/national-minerals-information-center/iron-ore-statistics-and-information#:~:text=Almost%20all%20(98%25)%20iron,one%2Dthird%20of%20total%20exports
BRITANNICA KIDS: https://kids.britannica.com/kids/article/ore/601319#:~:text=Deposits%20of%20ore%20are%20located,minerals%20are%20galena%20and%20sphalerite