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Igneous rocks are an integral part of all rocks that make up our planet; that is why there are a lot of interesting facts to be shared. Igneous rocks are one of three members of rock types. Igneous rocks are initially crystallized from magma or lava.
Igneous rocks have unique chemical and mineral compositions. They can be a source of rare elements of almost imperceptible concentrations and make huge breathtaking landscapes. They are formations, which can tell the age of mountain ranges formation and which can serve you as a kitchen tabletop.
Diamonds are mined from igneous rocks called kimberlites. Igneous rocks are a source of precious and base metals, rare earth elements, and gemstones. We would like to share some interesting, fun, and scientific facts about igneous rocks, which will not leave anyone indifferent.
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Interesting Fact: Diamonds are extracted from igneous rocks.
Kimberlites are extrusive igneous rock (e.g., a volcanic rock) that transport diamonds from 150-700 km depths in a rare volcanic eruption of a kimberlite magma. Luckily, since diamond is the hardest mineral, it can usually survive such rough handling. Kimberlite may occur in the field as dikes or pipes.
Kimberlite is the name given to a silica-poor and magnesium-rich extrusive igneous rock (e.g., a volcanic rock) that contains major amounts of olivine, often serpentinized. It is a highly variable mixture of melt, minerals crystallizing from the melt, and foreign crystals and rock pieces.
On their turbulent journey upwards, magmas assimilate other types of minerals, collectively referred to as xenoliths (Greek for “foreign rocks”). The xenoliths found in kimberlite include diamonds. The vast majority of the diamonds mined in the world today are found in kimberlite rocks.
Cool Fact: Geodes are formed in igneous rocks.
Geodes – a spherical geological formation, with a hollow inside lined with crystals, are usually found in volcanic igneous rocks with andesitic and dacitic composition mostly. The inner part of the geode reveals perfectly formed crystals of rock quartz and amethyst growing towards the center of the hollow.
Voids, which will be a geode in the future, are formed during magma uplift from beneath the earth to the surface. Some gas bubbles had not enough time to escape from the lava flow and solidified inside, providing a space for crystal growth.
Groundwater or low-temperature hydrothermal solutions precipitate in voids forming crystals growing towards the center of the void. The most common crystals found inside a geode are quartz and its purple variety amethyst.
TIP: Geodes are one the most popular rocks among rockhounds. Geodes can be quite valuable. Find out the real value of geodes in the article below:
The Value of Geodes: Are They Worth Anything?
Fun Fact: Igneous rocks can create surrealistic landscapes.
Basalt, as volcanic igneous rock, can create unrealistic landscapes that fascinate people all over the world.
Due to the rapid cooling of the basaltic lava and its specific chemical composition, that type of volcanic igneous rock solidifies in a special hexagonal geometrical shape called columnar jointing. Svartifoss waterfall, Stuðlagil canyon, and Reynisfjara beach in Iceland are the most breathtaking examples.
Iceland basalt columns are the result of this rapid cooling process that changes the chemical makeup and appearance of the lava. Basalt volcanic rock has a special geometrical shape due to this change in composition.
The basalt pillars and hexagonal rock formations you can observe in Iceland have a special feature called columnar jointing. This is what gives each basalt column their unmistakable hexagonal shape and makes them so neat to look at.
Interesting Fact: The best igneous rock for road construction.
Previously described basaltic rock (extrusive igneous rock) – is a very popular material for paved roads construction. Since ancient Roman times, when Roman engineers used basalt to pave a lot of Roman roads, till the present day, basalt is the most common construction material for paved roads.
Scientific Fact: Pegmatites are a source of giant gemstones.
Pegmatites are crystalline igneous rocks that are distinguished by their large-size crystals. The gem minerals occur in open cavities or “pockets” within the pegmatite. The largest crystals ever found have come from pegmatites: 18-m-long beryl crystal and a 300-kg transparent gem topaz.
As the main magma body cools, water originally present in low concentrations becomes concentrated in the molten rock because it does not get incorporated into most minerals that crystallize.
Consequently, the last, uncrystallized fraction is water-rich. It is also rich in other unusual elements (lithium, beryllium, boron) that also do not like to go into ordinary minerals.
When this unusual magma is expelled in the final stages of crystallization of the magma, it solidifies to form a pegmatite.
The high water content of the magma makes it possible for the crystals to grow quickly, so pegmatite crystals are often large. Of course, this is important for gem specimens formation also!
TIP: Three main types of rocks exist on the Earth. Sedimentary, metaporphic and igneous rocks. Do you know what the differences between sedimentary and igneous rocks are? Check them out in the article below:
Sedimentary vs. Igneous Rocks: Differences & Similarities
Scientific Fact: Igneous rocks are a source of metals.
It’s not a surprise that igneous rocks have a high mining potential. They are so essential for industry and science, so it would be a crime not to mention their metal potential here.
Igneous rocks are also a source of precious and base metals. Platinum, palladium, and chromium are commonly extracted from mafic-ultramafic igneous rocks. Granitic igneous rocks can be perspective for tungsten extraction. Rhyolites can be a source of tin. Rhyodacite and dacite have uranium potential.
Fun Fact: Texture of igneous rock, which looks like a plant.
Spinifex textures are a striking feature of ultramafic to mafic igneous rocks. The texture has a superficially similar appearance to spinifex grasses (Trioda sp.), after which the texture was named. It is typical for rocks where the olivine or pyroxene crystals cool in the presence of a thermal gradient.
Spinifex textures are largely restricted to Archean komatiites and komatiitic basalts – igneous rocks. Komatiite samples are of great scientific value because they are extremely rare.
Weird Fact: Igneous rocks formation time.
How long does it take for igneous rock to form? We will give you a response, however, you will be surprised by the period.
Intrusive igneous rocks, which solidify deep beneath the surface, can be formed from thousands to millions of years. Extrusive (volcanic) igneous rocks can be formed rapidly. It can take from 20 minutes up to several days for extrusive rocks, which are formed as a result of lava cooling on the surface.
BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):
- Smithsonian Handbooks: Rocks & Minerals
- Gemstone & Crystal Properties (Quick Study Home)
- Ultimate Explorer Field Guide: Rocks and Minerals (National Geographic Kids)
Cool Fact: Igneous rocks in your kitchen.
Igneous rocks have several physical properties that ideally fit to be used in interior and functional constructions.
Even though igneous rocks have high mineral and gemstones potential, they can be also used in a design. Igneous rocks are extremely hard, durable, and aesthetically pleasing, so they can be widely used as a countertop or tiles in your kitchen. Granites, gabbros, and anorthosites rocks are commonly used rocks.
TIP: Do you know what the main characteristics of igneous rocks? Check their main characteristics in the article below:
The 6 Main Characteristics of Igneous Rocks
Weird Fact: Floating rocks.
The lightest rock on the earth, which can float on the water surface, is pumice. Pumice is a fine-grained volcanic igneous rock, which contains a lot of empty gas bubbles – vesicles. It is produced when lava goes through rapid cooling and loss of gases. It is very light grey to medium grey in color.
Pumice is also considered an extrusive (volcanic) igneous rock. Composition ranges from high-silica (rhyolitic) to low-silica (basaltic), but in most cases, pumice is in the rhyolite range.
Fun Fact: Pumice raft.
This fun fact is also related to pumice but categorized as fun because it is really hard to imagine a floating rocky island.
A pumice raft is a floating raft of pumice created by some eruptions of submarine volcanoes or coastal subaerial volcanoes. A very large pumice raft with an estimated area of 26,000 square kilometers appeared near New Zealand in August 2012. A possible source for the pumice was the Havre seamount eruption.
As we can see from the above, igneous rocks are not only the source of gemstones and precious metals but also a box of surprises.
Igneous rocks can form thousands of square kilometers of floating islands and can settle down in your house as a kitchen countertop. Igneous rocks can have intriguing unique textures, which resemble plants, and can form unbelievable surrealistic landscapes.
Igneous rocks are a primary source of diamonds and geodes. Both intrusive and extrusive igneous rocks are thoroughly studied by geologists and are extremely important to science. At the same time, they look so appealing, so artists commonly use them to create some art objects.
We are not mistaken when we say that igneous rocks are present in almost every sphere of our life.
We are constantly using rare elements extracted from igneous rocks as conductors and battery elements of our mobile phones. Do you still want to disagree? Please, look down. Most probably, you are staying on granite or basalt.
TIP: Do you know what the rarest gemstones on the Earth are? You will be suprised when you check them. Find out more in the article below: