Iceland’s volcanic landscape produces a surprisingly rich assortment of gemstones and collectible minerals, from transparent calcite crystals that helped establish modern optics to agates, zeolites, obsidian, and opal deposited by geothermal springs. The island sits on the Mid-Atlantic Ridge, where tectonic plates pull apart and magma continuously rises to the surface. That combination of fresh basaltic rock, abundant groundwater, and geothermal heat creates ideal conditions for mineral formation in gas cavities, lava tubes, and hydrothermal veins scattered across the country.
Iceland Spar, the Island’s Most Famous Crystal
If Iceland can claim a single gemstone contribution to world history, it is Iceland spar, an unusually pure and transparent variety of calcite. A site at Helgustadir in eastern Iceland supplied large quantities of clear calcite rhombs from 1668 to 1925, and those crystals played a major role in the early development of wave optics, crystallography, and crystal physics.1Journal of Geoscience Education. Iceland Spar: the Helgustadir Calcite locality and its influence on the development of Science In the late seventeenth century, the Danish scientist Rasmus Bartholin and the Dutch physicist Christiaan Huygens studied a curious property of these crystals: they split a single beam of light into two, producing a double image of anything viewed through them. Clear specimens of this type have been known as “Iceland spar” since around 1780.2History of Geo- and Space Sciences. Iceland spar and its legacy in science
The double-refraction property, called birefringence, eventually became one of the most important tools physicists had for understanding the wave nature of light. Calcite in general is extremely common worldwide, but the Helgustadir deposit was exceptional because it produced pieces large enough and clear enough for laboratory use. After the mine closed in 1925, Iceland spar became a collector’s item rather than a scientific supply. You can still find calcite crystals in Iceland today, though pieces rivaling the old Helgustadir specimens in clarity are rare. Smaller calcite formations occur in lava tubes and geothermal areas across the island, where mineral-rich water seeps through cracks in basalt and deposits calcium carbonate as it evaporates or cools.
The “Sunstone” Legend
Iceland spar is often linked to the Viking “sunstone,” a crystal mentioned in medieval Icelandic sagas as a tool for finding the sun’s position on overcast days. According to a widespread hypothesis, the Vikings may have navigated by detecting the polarization pattern of skylight through a birefringent crystal, and Iceland spar is the leading candidate for what that crystal could have been.3Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies The idea is appealing because it connects Iceland’s geology directly to Viking seafaring, and it has become a popular narrative in museums and documentaries.
The story deserves a healthy dose of skepticism, though. Research has challenged the notion that polarized skylight navigation under fully overcast skies has any scientific basis. One analysis concluded that the widely held idea should be treated with caution and that even under partly clear skies, the method is unreliable.4PubMed. Disputing Viking navigation by polarized skylight The sagas themselves are vague about what a sunstone actually was, and no confirmed Viking-age specimen has been recovered in an archaeological context definitively linked to navigation. It remains a tantalizing possibility rather than established fact, but it has certainly boosted public interest in Iceland spar as a gemstone with a story.
Obsidian and Volcanic Glass
Obsidian forms when silica-rich lava cools so rapidly that atoms do not have time to arrange into a crystal structure. The result is natural glass, usually jet black but sometimes streaked with bands of grey, brown, or a shimmering iridescence caused by tiny gas bubbles or mineral inclusions. Iceland has several well-known obsidian localities. The ridge called Hrafntinnuhryggur near the Krafla volcanic system in the northeast is one of the most accessible, where hikers can see glassy outcrops protruding from the surrounding landscape.
Obsidian is not a mineral in the strict sense because it lacks an ordered crystal lattice, but it has been valued as a gemstone, a toolmaking material, and a decorative stone for thousands of years. In Iceland, early settlers used locally sourced obsidian for cutting tools. Today it appeals mainly to collectors and jewelry makers. The pieces found in Iceland tend to be opaque black or translucent smoky grey; the “rainbow” and “fire” obsidians prized in the gem trade come from other volcanic regions. Still, a cleanly fractured Icelandic obsidian specimen has a dramatic glassy lustre that makes it a popular souvenir.
Zeolites at Teigarhorn and Other Eastern Localities
If you are interested in mineral collecting, the zeolite group may be the most rewarding family to study in Iceland. Zeolites are a class of hydrated aluminosilicate minerals that form when groundwater interacts with volcanic rock at low to moderate temperatures over long periods. They tend to crystallize inside the gas vesicles (small cavities left by trapped bubbles) of basaltic lava flows, and Iceland’s thick basalt sequences have produced world-class zeolite specimens.
The most celebrated locality is Teigarhorn in the Berufjördur area of eastern Iceland, where researchers have documented the progression of zeolite minerals that formed as basaltic lavas were gradually buried and heated during low-grade metamorphism.5American Journal of Science. Porosity evolution and mineral paragenesis during low-grade metamorphism of basaltic lavas at Teigarhorn, eastern Iceland Species found at Teigarhorn include stilbite, heulandite, scolecite, and several others, some of which form elegant radiating crystal clusters. The site is now protected as a natural monument, so collecting there is prohibited. Other spots along Iceland’s eastern fjords and in certain parts of the Westfjords produce similar zeolite species, though rarely of the same display quality.
Zeolites may not have the name recognition of diamonds or sapphires, but among mineral collectors they are highly sought after. Well-formed stilbite fans from Iceland can command respectable prices at mineral shows, and the variety of species available within a single outcrop makes these localities scientifically interesting as well.
Agate, Chalcedony, and Jasper
Like zeolites, agates form inside the gas cavities of basaltic rock, but through a different process. Silica-rich fluids slowly fill the cavity in successive layers, depositing microcrystalline quartz (chalcedony) in concentric bands. The result is the familiar banded pattern of agate, sometimes with a hollow center lined with tiny quartz crystals. Iceland’s older basalt formations, particularly those in the eastern and western fjords where erosion has exposed deep lava sequences, are the best hunting grounds for agates.
Icelandic agates tend to be modest in size compared to the enormous specimens found in some South American deposits, but they can display attractive banding in shades of grey, white, red, and occasionally blue. Jasper, an opaque variety of microcrystalline quartz colored by iron oxides or other impurities, also turns up in the same geological settings. Red jasper pebbles can sometimes be found on beaches where erosion has liberated them from their host rock. Chalcedony without obvious banding appears as well, often in pale translucent grey or milky white. None of these silica minerals are rare in a global sense, but finding them in Iceland’s young volcanic terrain is a reminder that mineral formation here happens on geologically fast timescales.
Opal from Geothermal Hot Springs
Iceland’s geothermal activity also produces opal, a hydrated form of silica that lacks the crystal structure of quartz. Research on silica sinters sampled from Icelandic hot-spring fields in the Reykholt region and at the Hveravellir site found opal forming across a wide range of water temperatures, from around 14 °C to 101 °C.6European Journal of Mineralogy. Near-infrared signature of hydrothermal opal: a case study of Icelandic silica sinters The texture and properties of the opal varied with the temperature of the spring, making these deposits scientifically valuable as natural laboratories for understanding how opal forms.
Most Icelandic opal is common opal rather than the precious “play-of-color” opal used in fine jewelry. Common opal can still be attractive, appearing as milky, translucent, or glassy coatings and nodules in geothermal areas. A glassy variety called hyalite sometimes fluoresces vivid green under ultraviolet light, which makes it a favorite among collectors who enjoy displaying minerals under UV lamps. Precious opal with spectral color flashes has not been reported from Iceland in significant quantities, so if you are hoping to find the next great opal field, Australia and Ethiopia remain better bets. But Iceland’s common opal deposits are noteworthy for what they reveal about silica chemistry in active volcanic environments.
Olivine and Peridot
Olivine is one of the most abundant minerals in the Earth’s upper mantle, and because Iceland’s basaltic magmas originate from mantle material, olivine crystals are common in fresh Icelandic lavas. Researchers studying the 2010 eruption of Eyjafjallajökull, for example, used olivine crystals in the basalts to reconstruct the timescales of magma storage and migration beneath the volcano.7American Mineralogist. Timescales of magma storage and migration recorded by olivine crystals in basalts of the March–April 2010 eruption at Eyjafjallajökull volcano, Iceland These crystals are typically small, greenish grains embedded in dark basalt, visible with the naked eye but not usually gem quality.
The gem-quality version of olivine is called peridot, and it requires crystals that are large, transparent, and relatively free of fractures. Iceland does produce occasional peridot-quality grains, but not at the scale or quality of the classic sources in places like the Arizona desert or the Red Sea island of Zabargad. What you are far more likely to encounter is “olivine sand,” a phenomenon found on certain Icelandic beaches where wave action concentrates the green mineral grains into greenish patches. The beaches near Vik and along parts of the Snaefellsnes peninsula sometimes show this effect. It is not gem-grade material, but it is a striking sight and a direct link between the gemstone in a jeweler’s case and the raw geology of a volcanic island.
Quartz and Hydrothermal Vein Minerals
Crystalline quartz, the transparent six-sided prisms that most people picture when they hear the word “crystal,” is less common in Iceland than you might expect. Basaltic rock is relatively low in silica compared to the granites and metamorphic rocks that produce quartz veins in many other countries. Still, quartz does form in Iceland’s geothermal systems, where hot fluids circulate through fractures in the rock and deposit silica as they cool. Research on a fossil geothermal system in southwestern Iceland has documented vein quartz produced by hydrothermal alteration of the surrounding basalt.8Goldschmidt2021 abstracts. Hydrothermal alteration as source for vein quartz in a fossil geothermal system in SW Iceland
Alongside quartz, hydrothermal veins in Icelandic basalt can carry epidote, a pistachio-green mineral that forms during low-temperature alteration of iron- and calcium-bearing rocks. Epidote is not widely known as a gemstone, but when it occurs as well-formed crystals it can be quite attractive and is collected by enthusiasts. Prehnite, another pale green mineral, shows up in similar settings and is occasionally cut as a cabochon for jewelry. These hydrothermal minerals tend to be found wherever old geothermal systems have become inactive and been exposed by erosion, particularly in the Tertiary basalt formations of the Westfjords and eastern Iceland.
Minerals Inside Lava Tubes
Iceland’s lava tubes add another dimension to the island’s mineral diversity. When a basaltic lava flow crusts over on top while molten rock continues to drain underneath, it leaves behind a hollow tunnel. Over time, groundwater seeping through the rock above can deposit secondary minerals on the tube walls and ceilings. Research in Icelandic lava tubes has identified copper-rich secondary minerals forming from localized copper enrichments in the groundwater, likely originating from overlying ash deposits and nearby volcanic formations.9Earth and Space Science. A Study in Blue: Secondary Copper‐Rich Minerals and Their Associated Bacterial Diversity in Icelandic Lava Tubes These copper minerals can appear as vivid blue and green coatings, sometimes associated with microbial mats that contribute to their formation.
Beyond the copper minerals, lava tubes elsewhere have been documented to host calcite stalactites, opal-like silica deposits, and gypsum crusts, all formed when seepage water dissolves minerals from the surrounding rock and then becomes supersaturated as conditions inside the tube shift.10PubMed Central. Multitechnique characterization of secondary minerals near HI-SEAS, Hawaii, as Martian subsurface analogues Iceland’s lava tubes, such as those in the Hallmundarhraun lava field, are known for delicate mineral formations that visitors can see on guided tours. These are not gemstones you would mount in a ring, but they represent some of the most visually striking mineral occurrences on the island.
Practical Realities of Gemstone Hunting in Iceland
Before you pack a rock hammer, there are some ground rules worth knowing. Iceland takes the protection of its natural features seriously. The Nature Conservation Act restricts the collection of rocks, minerals, and fossils from protected areas, and many of the best mineral localities, including Teigarhorn, fall under legal protection. In unprotected areas, casual collecting of loose surface material is generally tolerated, but breaking rock from outcrops or using heavy tools can draw attention from landowners and authorities. If you plan to collect, it is wise to ask locally and respect posted signage.
The eastern fjords are the most mineralogically productive part of the island for surface collecting, because deep erosion has exposed ancient lava sequences full of vesicles and veins. The Westfjords offer similar geology but are more remote and less visited. The younger volcanic zones in the center and south of the country produce fresh olivine, obsidian, and geothermal minerals, but the rock is often too recent and intact to have released many loose specimens. Beaches everywhere can yield tumbled pebbles of agate, jasper, and chalcedony, and checking gravel banks after storms is a time-honored strategy.
If you are visiting Iceland and want to see quality mineral specimens without the fieldwork, several museums display excellent collections. The Petra Stone Collection in Stödvarfjördur, assembled by a local resident over decades, features agates, zeolites, jasper, and other minerals all sourced from the surrounding countryside. The Icelandic Institute of Natural History in Reykjavik holds the national mineral collection, including historic Iceland spar specimens. These collections give a good sense of what the island produces and where the most promising areas lie for anyone inclined to explore further.
Why Iceland Punches Above Its Weight in Mineral Variety
For an island made almost entirely of basalt, Iceland hosts a wider variety of interesting minerals than its simple geology might suggest. The explanation comes down to water. Iceland receives abundant rainfall, sits on an active volcanic system that heats groundwater to high temperatures, and has thick basalt sequences riddled with cracks and gas cavities that give fluids plenty of space to react with rock and deposit new minerals. Every hot spring, every lava tube, every ancient fracture zone is a small-scale chemical factory converting dissolved elements into solid crystals. The result is not a traditional gem-mining destination, but a place where a geologically literate visitor can find examples of dozens of mineral species without ever leaving the island’s young volcanic terrain. For anyone drawn to the intersection of geology and gemstones, Iceland offers something that the classic tropical gem sources do not: a chance to see where minerals are actively being made.