The Metamorphic Identification Lesson:
It is posted! The Metamorphic Rock Identification Lesson is now for sale on my TpT website. It is very similar to the igneous rock and sedimentary rock lessons I have had posted for some time in my store. These lessons have been used in the classroom and have been tweaked many times over the years. I am confident that you will find them to be very useful and straightforward. Metamorphic rocks are easier for students to identify than igneous or sedimentary rocks. In my opinion, this is due to the fact that there are only two textures for metamorphic rocks. Igneous rocks have four primary textures and multiple secondary textures and sedimentary rocks have three textures. Simply having two textures, makes it much easier for students to accurately identify the name of the rock.
Foliated Metamorphic Rocks:
The first texture is called foliated. Foliated rocks have undergone the addition of heat and pressure at great depth due to regional metamorphism. Keep in mind that not enough heat has been added to melt it; this would form an igneous rock. Adding pressure to a rock causes the minerals to become aligned perpendicular to the direction of the pressure. This gives the rock the appearance of “layering”, however, the correct term in metamorphism is banding. Any minerals that are elongated in their crystal shape will all align themselves parallel or paralle“lish” to each other. This can take the form of the rock looking flat, it might have long, thin needles of minerals that you can see (most commonly amphibole, muscovite and biotite). If more heat and pressure is added, you can end up with porphoblasts which are large crystals within the rock, larger than the other crystals that are visible. Typically, these porphoblasts are of the minerals garnet, staurolite or amphibole. If additional heat and pressure are added you can end up with the metamorphic rock, gneiss. Gneiss has banding of minerals that are differentiated by color, either black-and-white banding, or pink and black banding. Often times gneiss is formed directly from granite which can be easily identified by students. The pictures included with this blog are of the metamorphic rocks gneiss and garnet schist (containing porphoblasts).
Nonfoliated Metamorphic Rocks:
If the rock consists of only one mineral prior to metamorphism, then foliation will not occur. This second texture of metamorphic rocks is called nonfoliated. These rocks will not appear flat, banded, or have elongated minerals visible to the eye. They tend to be blocky, and they might have a sugary appearance. There are three main rocks that are non-foliated: marble, quartzite and anthracite coal. Marble is made of calcite which means the rock was originally limestone or dolomite. Quartzite is made of a sandstone that has been metamorphosed, and anthracite coal is the type of coal consisting of highly altered plant remains.
Hints for Students to Pronounce Metamorphic Rocks:
Another reason metamorphic rocks seem to be easier to identify is that there are fewer rock names: slate, phyllite, schist, gneiss, marble, quartzite and anthracite; a grand total of 7 metamorphic names! However, they can be difficult to pronounce correctly due to their unique spelling! There are a couple of goofy hints that I give to students to help them pronounce and identify these metamorphic rock names.
- The rock GNEISS is pronounced “nice”, so I show them pictures of T-shirts for geologists that say “have a gneiss day”.
- I also tell them that gneiss tends to be striped like a zebra either black-and-white stripes or pink and black stripes. It’s a very distinctive rock that most people can identify very quickly once they learn this information.
- Phyllite is often mispronounced, so I like to tell the students that this is “the rock named Phil”. “Can you identify Phil”?
What is included in the Metamorphic Rock Identification Lesson?:
When teaching metamorphic rocks, it is very important to have the students collaborate. So, this lesson that is for sale on metamorphic rocks includes PowerPoint notes that are very succinct and clear with a focus-note guide that the students can fill in as they follow along with the notes. In addition, there is an identification chart and a blank answer page to fill out as they try to name the rocks. I always recommend the students use a pencil, so that when they make mistakes, which they will, they can come back and correct their answers later.
Be sure to have sets of metamorphic rocks for students to identify for this lesson.
I am very proud of these rock identification lessons that I have for sale, I hope that they are as useful to you in the classroom as they have been for me! If you are just discovering this blog, please note that I have very similar lessons on igneous rocks and sedimentary rocks already for sale in my MidnightStar TpT site. Coming soon will be a bundle of my igneous, sedimentary and metamorphic identification lessons along with review worksheets on all three topics combined. Stay tuned for my next blog.