Geek Pocket Minecraft - Web Site Smaller Banner    Minecraft Themed Igneous Rocks Lesson

Let's pretend we've entered the Nether just in time to see a witch melting rocks to make lava. She's going to mix it all up, then let it cool and harden into new rocks. These are called igneous rocks.

Witch melting rocks to make lava/magma

But first, the ingredients. What rocks does she throw in here lava stew? Well, whatever rocks happen to be around, any kind, all kinds - whatever is in the immediate area. In Minecraft, that's netherrack and quartz (and sometimes soul sand or gravel). In real life, it can be anything - igneous, sedimentary, metamorphic, crystals, or whatever. The possibilities are endless, but most of the batch ends up being some or all of these 6 most common minerals that are found in the earth's crust. Also note that in real life, there isn't a huge Nether cavern or a witch, but it's rock deep in the earth that is turning in to lava due to heat and pressure. Lava that is still deep underground is called magma.

Lava/Magma Most Common Ingredients:

LIGHT COLOR
"Felsic" Minerals
Minecraft Nether Quartz
                  Block
Quartz
("Nether Quartz")
Minecraft-inspired Albite
                  Block
Albite
(Plagioclase Feldspar)
Minecraft-inspired
                  Orthoclase Block
Orthoclase
(Potassium Feldspar)
DARK COLOR
"Mafic" Minerals
Minecraft Inspired Biotite Block
Biotite
(Dark Mica)
Minecraft Inspired Hornblende Block
Hornblende
(Amphibole)
Minecraft Inspired Augite
                  Block
Augite
(Pyroxene)

MEMORY AID: "Quick, Acquire Oranges Before Having Apples"

The colors shown are typical but can vary a lot. For example, orthoclase can be white, but it's often pink due to iron "impurities" in it. But, for the purposes of this tutorial, these are the 6 most common minerals and most common colors. So if you find a rock with pink in it, you can call it orthoclase, and you will usually be right. If you were working for a mining company, you'd want to do all the tests - hardness, crystal shape, scratch test, microscope view, etc. But for having fun finding rocks, orthoclase is close enough - don't stress out too much about it!

The most important part is light vs. dark. The lighter minerals are more common in the continental crust (land), and the heavier, darker minerals are more common in the crust under the ocean. However volcanoes can form near the ocean and spew out the darker stuff, so you can pretty much find both light and dark everywhere.

Now, mix all of the rocks and minerals together in a big lava "stew" and let it cool. What you get depends on how much of each mineral there is, and, interestingly, how slow or fast it cooled and solidified into stone. If the lava (actually magma) cools underground and never reaches the surface, it cools slowly, which means it has time to grow crystals. Not usually huge ones, but about 1mm "specks" you can see without squinting. These are plutonic rocks. If the lava escapes from a volcano, it cools very quickly and forms only tiny crystals (or even none at all, as well see in a bit). In this case the rock appears more evenly mixed.

Real life rhyolite vs. granite

Below are the 6 basic types of igneous rocks. Three of these currently appear in Minecraft (andesite, diorite, and granite).

"Crafted" Basic Igneous Rock Types:


LIGHT COLOR / "Felsic"
Few dark specks
INTERMEDIATE COLOR
MANY dark specks
DARK COLOR / "Mafic"
Mostly dark
VOLCANIC
Tiny Crystals / More Uniform
Minecraft Inspired Rhyolite
                  Block
Rhyolite
Minecraft Andesite Block
Andesite
Minecraft Inspired Basalt
                  Block
Basalt
PLUTONIC
Large Crystals / Specks
Minecraft Granite Block
Granite
Minecraft Diorite Block
Diorite
Minecraft Inspired Gabbro
                  Block
Gabbro

MEMORY AID: "Read And Believe Geology Does Good"

Again colors may vary. For this chart though, go more by light-medium-dark. So, for example, if you find a white rock with black specks, don't automatically assume it's diorite. If there's not that many, call it a white granite. If it looks like someone took a black marker and dotted the rock all over, that's diorite.

Real life granite vs. diorite

SPECIAL TYPES:
Minecraft Obsidian, Pumice, and Scoria Blocks in triangular volcanic rock chart

If the "lava escaping from a volcano" cools SUPER fast, it may form no crystals at all, making an opaque glass called obsidian. Interestingly, even though it is formed from some of the lighter minerals, it usually appears black. (Basaltic glass is also possible but rare.)

If the "lava escaping from a volcano" cools instantaneously, like from an explosive eruption (like Mt. St. Helens), the steam and gases present in the lava won't even have escaped yet before the rock hardens, so you get a rock riddled with holes. If light in color, it's pumice; if dark, it's called scoria. Sometimes scoria is used as a decorative rock in landscaping:

Scoria from a landscaping bed at Coldwater (Michigan) High School

Have fun!!! 

Minecraft has inspired me to get interested in geology again. I was interested as a kid, but the books made it way complicated. There is a place for that... after all, geologists need to know all the countless variations, but that's too much for the average person. In real life every rock is unique. One of the appeals of Minecraft is its uniformity - i.e., each block is exactly the same size, and granite always looks identical. We can "Minecraftize" real life to some extent to boil rocks down to some basic types. Yes, there are many more types, and there are many variations within a type, but we can start with just the basic blocks just presented, in a fun and easy to memorize way, and then look for these basic types in real life. What fun it is, for example, to find a real diorite rock after having used it countless times in the game!

Microsoft and Mojang are working on an "educational" version of Minecraft. I hope that someday they will add at least some of these missing basic blocks to the game - just think of how easy and exciting it will be to teach geology if they do!


This page last updated 08/19/2016. Web site content (C) 2016 Kevin Jay North. Free for personal use; do not copy to other websites without permission.
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