Andesite is a pale to dark gray lava rock with white and black speckling. The speckles are crystals such as feldspar and quartz. If you’re currently standing on land, the Earth’s continental crust, most of the rock holding you up is andesite rock!
Is andesite a gem? It depends on how you define gemstones. Andesite isn’t a mineral but a rock (composed of two or more minerals). Not all gemstones are minerals, though. Since andesite can be used in jewelry and decor, we classify it as a gemstone.
Alright, well is andesite a crystal? No, andesite isn’t a crystal, but it does contain crystals! One of the most notable ones is andesine (or andesine feldspar), a red, green, yellow, or color-changing gemstone discovered in 2003.
Today, you’ll learn all the information you need on andesite gemstone uses, healing properties, characteristics, and more!
Andesite is a semi-precious gemstone with a neutral, salt-and-pepper appearance to match any outfit. Besides adornment, what is andesite used for?
Builders often use andesite stones for road gravel, bridges, and railroads. If you’ve ever seen the support beams along train tracks called railroad ties, the stones holding them up were probably andesite!
Geologists and astrogeologists have gained valuable insights from andesite stones. One example came in 2009, when researchers in Antarctica found the only known andesite meteorites on Earth, broadening the understanding of our Solar System.
Another fascinating piece of evidence we can thank andesite for is its ties to Mars. Research from 2011 revealed andesite could be part of Mars’s crust, which would prove Mars has or had volcanic activity.
On the personality side of the cosmos, andesite is a zodiac stone for Scorpio and Aries. Given both signs are traditionally ruled by Mars, it makes sense!
Now, what are the characteristics of andesite?
Andesite rocks are igneous and very similar to basalt, but with paler coloring, less iron, and less magnesium. The amount of silica in andesite is between rhyolite and basalt.
If you know about igneous rocks, you may wonder: is andesite intrusive or extrusive? Andesite is an extrusive volcanic rock, meaning it forms after hot, liquid magma reaches Earth’s surface (outside the volcano) and hardens.
Andesite’s composition is mostly plagioclase feldspar, pyroxene, and hornblende. As an intermediate rock, it’s made up of 52-63 percent silica. The feldspar content is at least 65 percent plagioclase. Other common andesite minerals are magnetite, quartz, sphene, biotite, and olivine.
The mineral crystals inside andesite may vary in size and appearance based on andesite’s texture. The stone can be aphanitic (fine-grained crystals too small to see with the naked eye), porphyritic, or vesicular.
Porphyritic andesite is fine-grained but also contains larger, visible crystals called phenocrysts throughout. Andesites with this combination of tiny and large crystals are also called “andesite porphyry.” However, if one mineral makes up the majority of the stone’s phenocrysts, like garnet for example, it may go by “garnet andesite.”
Less common vesicular or amygdaloidal andesites have larger pockets (vesicles) filled with secondary minerals (formed later through weathering) like quartz, calcite, or chalcedony.
You can find andesite’s properties listed below:
Color: Light to dark gray, sometimes bluish or reddish; Crystals inside are usually black, white, or tan but can be various other colors
Crystal structure: None
Luster: Resinous; Portions may be vitreous (glass-like)
Now, what are the main andesite rock subtypes?
Andesite isn’t just a rock, but a rock family. Most andesites are pyroxene andesites, which are denser and darker than other types. Besides pyroxene andesites, the three most common subtypes of andesite are:
Hypersthene Andesites: Often brown and gray subtype with predominantly hypersthene inclusions, which occur in thinly layered masses throughout
Hornblende Andesites: Yellow, light pink, or gray feldspar-rich subtype
Quartz Andesites (Dacites): Gray, blue-gray, or black silica-rich rocks with 20 percent quartz (not always classified as andesite subtype)
With the mineralogy covered, let’s jump into andesite’s past and metaphysical side!
Andesite symbolizes balance, diplomacy, and sophistication. It can also represent stability and intellect.
German geologist and paleontologist Christian Leopold von Buch first named andesite in 1826. The name comes from the stone’s abundant location: the Andes Mountains in South America.
One famous example of andesite in modern history is the controversial Ica stones.
Image Credit: By Brattarb - Own work, CC BY-SA 3.0
The Ica stones are a collection of carved Peruvian andesite rocks found in the Ica Province, formerly believed to be ancient artifacts.
A Peruvian doctor named Javier Cabrera Darguea started collecting the stones in the 1960s. Darguea got around 300 Ica stones from brothers Carlos and Pablo Soldi and thousands from a farmer named Basilio Uschuya.
Some of the stone’s images were simple, like fish and flowers. Other carvings depicted groundbreaking images of dinosaurs and humans living together, advanced technologies, and modern medical procedures. Many designs matched the artistic style of ancient Inca, Paracas, Tiwanaku, and Nazca cultures.
Overall, the stones were thought to be evidence of modern knowledge or practices that had never been depicted in art from ancient time periods before. Darguea studied the Ica stones for forty years, eventually publishing theories about mankind being millions of years old or being created by aliens.
However, throughout the 1970s, Uschuya made multiple claims about the stones’ authenticity. He first claimed they were forgeries, then later recanted this claim, but eventually confirmed their hoax status in 1977 by showing how he created them.
While the stones may not be true ancient artifacts, their twisting story certainly made an impact through the late 20th century. Some conspiracy theorists still point to the stones as evidence of ancient aliens or ancient myths being true.
If you practice the ancient art of crystal healing, however, you may wonder what powers andesite has. We’ll tell you!
Image Credit: By Stanislav Doronenko - Own work, CC BY 3.0
Andesite, like all gemstones, can function as a healing stone for various purposes. Along with other gray gemstones, andesite can provide balance, grounding, and greater perspective. Additionally, gray gems like andesite are great chakra stones for the root chakra.
What about andesite’s powers for physical and emotional healing?
Andesite is said to be helpful in protecting accident-prone folks from injury. Already injured? The stone can also speed your recovery.
Crystal healers use andesite to treat muscular and bone disorders. Many also believe the stone can help those who are ill identify the underlying issue or disease causing their symptoms.
Ever have racing thoughts you wish would just slow down? Or anxious rumination that’s difficult to shut off? Porphyritic andesite stones are believed to help soothe restless minds.
Other purported benefits of andesite include better willpower, more motivation, and greater mental clarity.
Andesite quality and value isn’t graded the same as other gemstones. Overall, porphyry andesite tends to have higher value than aphanitic andesite, but not by much.
Still, andesite’s value may be influenced by its color and cut.
Geologists divide igneous rocks like andesite into four color classifications: mafic, ultramafic, felsic, and intermediate. As an intermediate stone, andesite color is medium to dark in color and usually grayish. It has 15-40 percent dark-colored minerals. The rest of its composition is light-colored minerals.
The common phenocrysts are pale gray to white plagioclase feldspar and black stones like biotite or hornblende. Other minerals can cause reddish, tan, or bluish-gray hues.
Andesite is tricky to cut. While hard and durable, it’s also more porous than other rocks. Typically, gem cutters saw the stone with a segmented circular diamond saw blade.
Most andesite gems are slabs, beads, cabochons, polished freeform pieces, or tumbled stones. Most andesite jewelry has beads or cabochons, though some pendants have unique carved or tower shapes. You may even see vial pendants holding tiny fragments of raw andesite.
Speaking of the raw material, how is andesite formed?
Image Credit: By Photographer: Siim Sepp, 2005 - Own work, CC BY-SA 3.0
Andesite’s formation occurs around volcanoes. It can form through a few processes, all of which involve magma. However, the general process is virtually the same.
First, hot, liquid magma erupts and lands outside the volcano. It cools rapidly, resulting in its fine-grained texture. If the right mineral ingredients are present in the magma, the larger phenocrysts will crystallize inside the solidifying mass.
After the rock solidifies, it may undergo weathering from environmental forces. This weathering can sometimes alter the chemistry of certain minerals inside the stone, creating secondary minerals.
Most andesite occurs in the continental crust (the top layer of Earth that makes up our continents) and subduction zones. Subduction zones, like the Andes Mountains, are areas where tectonic plates converge, meaning one plate moves under the other and curves down into the hot mantle layer.
Another type of area filled with andesite is island arcs, where volcanoes form a chain along areas where lots of earthquakes happen. One famous island arc is the Ring of Fire that borders most of the Pacific Ocean.
Nation-wise, where is andesite found?
You may have already guessed that most andesite comes from the Andes Mountains. Another mountain range abundant in andesite is the Cordillera mountains across North America and Central America.
New Zealand boasts multiple areas with andesite, like the Great Barrier Islands, Coromandel Peninsula, and Raglan-Kawhia area.
Active volcanoes with andesite nearby include:
Banai-san and Mount Fuji in Japan
Krakatoa in Indonesia
Montagne Pelée and Soufrière Saint Vincent in the Caribbean
Mount Adams, Mount Hood, and Mount Shasta in the USA
Mount Ngauruhoe in New Zealand
Popocatépetl in Mexico
How much will andesite gemstones cost you? That’s next!
Andesite is an incredibly affordable gemstone. A 1-kg (2.2-lb) rough specimen is typically only $10-$30. Meanwhile, you can find 3-packs of 1” to 2” rough andesites for only $10 total!
Cabochons and palm stones are about $10-$15, though intricate carvings may raise the price. Most andesite pendants are around $15, but range from $1-$40. Higher-priced pendants may be porphyry andesite or have additional design elements like wire-wrapping. Bead strands will usually cost about $15-$20.
Andesite is a durable stone, so gemstone care here isn’t too complicated. To clean andesite, simply washing the stone with warm, soapy water and drying it with a microfiber cloth will do the trick.
For rough andesite that needs more work, you can soak it in soapy water for a day, then use a toothbrush to wipe the loosened dirt. You can also apply a more abrasive toothpaste (e.g. containing baking soda) to remove debris from trickier spots.
Store andesite stones away from other gemstones and rocks to prevent scratching or damage. You can even keep it in its own glass case to display!
Andesite rocks may not be what you first think of for gemstones, but that’s part of their charm. After all, how many people do you know that can say they’re wearing something that used to be lava?
Origins aside, andesite gemstones are an accessory to match anything and everything, along with bringing the grounding and balance you need to thrive!
Was this article helpful?