The Scientific Journey of Amethyst: The Truth Behind Crystals

Amethyst , a semi-precious crystal with its captivating purple color, has captivated since ancient times. It is known both as a popular ornamental stone in the jewelry world and is believed to possess various healing properties in alternative beliefs. However, the true value of amethyst lies not only in its cultural and historical significance but also in the geological and chemical facts behind it, which we might call amethyst science . This article will provide a comprehensive overview of amethyst's chemical and physical properties , geological formation processes, the scientific reasons for its purple color, and its applications in technology. We will explore the truth behind crystals, guided by scientific research and reliable sources.

Chemical and Physical Properties of Amethyst Stone

Amethyst is a type of quartz with the chemical formula silicon dioxide (SiO₂) ( Amethyst - Wikipedia ). In other words, amethyst is a purple variation of colorless quartz, whose primary components are silicon and oxygen. Trace amounts of impurities like iron (Fe) give this quartz crystal its unique purple color (more on this below).

Physically, amethyst has the durability and hardness typical of the quartz family. Its Mohs hardness is measured at 7, making it highly scratch-resistant ( Amethyst - Wikipedia ). Its density (density) is around 2.65 g/cm³ , the same as pure quartz ( Amethyst - Wikipedia ). Amethyst has a vitreous luster and, regardless of color, is white in powder form (white streak color) ( Amethyst - Wikipedia ). It may exhibit a weak, though not very pronounced, pleochroism (a slight variation in shades of purple when viewed from different angles) due to structural defects in the crystal ( Amethyst - Wikipedia). Because it lacks any distinct cleavage plane, it fractures with irregular, conchoidal (oyster-shell-like) fracture surfaces (Amethyst - Wikipedia ).

In terms of optical properties, amethyst is a uniaxially positive mineral, meaning it has a specific birefringence value that causes light to double as it passes through the crystal. The birefringence for quartz is approximately 0.009 and similar for amethyst ( Amethyst - Wikipedia ). The refractive index of amethyst ranges from about 1.54 to 1.55 ( Amethyst - Wikipedia ). These values, which represent how much light slows down as it passes through an amethyst crystal, are nearly identical to other varieties of quartz. Like all quartz, amethyst is piezoelectric , meaning it generates electric charges when mechanical pressure is applied ( Amethyst - Wikipedia ). This property is the fundamental principle that allows quartz crystals to be used as oscillators in electronic circuits, such as quartz watches and radio-frequency filters ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ).

In terms of its crystal structure, amethyst crystallizes in the trigonal crystal system and typically develops as hexagonal prismatic crystals ( Amethyst gemstone information ). The ends (terminations) of amethyst crystals are typically pyramidal and often exhibit well-formed surfaces. In nature, amethyst is typically found as large, polyhedral crystal clusters (druzes) or as geodes lining the interior surfaces of hollow rocks. Let's examine the geological processes that lead to the formation of these remarkable amethyst properties.

Amethyst Formation and Geological Processes

( File:Amethyst geode Planalto MNHN Minéralogie n2.jpg - Wikimedia Commons ) Figure: The interior surface of an amethyst geode from Brazil. Amethyst crystals typically grow by hydrothermal processes in cavities (geodic cavities) within volcanic rocks. This image shows purple amethyst crystals clustered together as dense druze on the cavity surface. Such geodes form as a result of the gradual precipitation of hot silica-rich solutions within the rock cavities.

Amethyst is a mineral that can form in various geological environments within the Earth's crust, but the most common formation mechanism is related to hydrothermal processes . Hot, mineral-rich fluids (hydrothermal fluids) generated by volcanic activity or geothermal heating deep within the Earth fill cracks and cavities. These hot fluids contain abundant dissolved silica (SiO₂) and may also contain small amounts of impurities such as iron and aluminum ( Amethyst | Properties, Formation, Gemstone » Geology Science ). At high temperatures, the silica in solution begins to crystallize in these cavities under favorable conditions (lowering pressure and temperature), and quartz precipitates. If trace elements in the solution and conditions are favorable, the resulting quartz crystals can be purple ( amethyst ). This process is generally slow and can take millions of years. Ultimately, the gas cavities within volcanic rocks (especially basaltic lava flows) transform into geodes filled with amethyst crystals. Amethyst geodes, many meters in diameter and filled with purple crystals, found in countries such as Brazil and Uruguay are striking examples of this process ( Study on the effect of heat treatment on amethyst color and the cause of coloration | Scientific Reports ).

Another formation scenario is the process called secondary deposition . In this case, cooler groundwater seeps into cracks in rocks and deposits the dissolved minerals it contains in these cavities ( Amethyst | Properties, Formation, Gemstone » Geology Science ). Silica-rich groundwater reacts with existing rocks, growing quartz crystals. If sufficient iron is present and the right conditions are met, as described in the following sections, this quartz becomes purple amethyst. Amethyst crystals are frequently encountered in fracture fillings and vein- type deposits in igneous or metamorphic rocks ( Amethyst | Properties, Formation, Gemstone » Geology Science ). For example, the amethyst deposits of Thunder Bay , Ontario, Canada, were formed by the formation of quartz crystals containing iron oxide (hematite) in ancient fracture fillings.

Amethyst generally forms near the surface in low-temperature environments. Geological studies have shown that amethyst crystals can often grow at temperatures below 100°C. Fluid inclusion analyses have revealed that crystals in some amethyst geodes indicate a formation temperature of ~75°C ( Amethyst from Newfoundland, Canada: Geology, Internal Features, and Fluid Inclusion Microthermometry ). These low temperatures suggest that amethyst formed at relatively shallow depths during the final stages of hydrothermal systems ( Amethyst from Newfoundland, Canada: Geology, Internal Features, and Fluid Inclusion Microthermometry ). However, amethyst formation is also possible in higher-temperature environments; for example, amethyst crystals have been reported in some pegmatite veins or during the final stages of regional metamorphism. In general, the presence of amethyst can provide clues about the geological history of the region. A geode filled with purple amethyst crystals is considered a sign of past volcanic activity and hydrothermal circulation in that area.

The Secret of Purple Color and the Scientific Explanation of Its Crystal Structure

Both the structural properties and the striking purple color of amethyst are related to the elements it contains and the atomic arrangement within its crystal lattice. In terms of its crystal structure , amethyst exhibits the atomic arrangement typical of quartz: each silicon atom is surrounded by four oxygen atoms, forming a SiO₄ tetrahedron . These tetrahedra share corners, creating a three-dimensional network (lattice) ( Amethyst - Wikipedia ). This three-dimensional framework of quartz is quite robust; because the bonds between atoms are strong, the crystal structure is rigid, which explains amethyst's high hardness and chemical resistance ( Amethyst - Wikipedia ). Amethyst crystallizes in the trigonal system and macroscopically appears as hexagonal prismatic crystals ( Amethyst gemstone information ). The pyramidal surfaces at the ends of these prismatic crystals reflect light, contributing to amethyst's lustrous and attractive appearance.

At the microscopic level, a structural defect called twinning is frequently found in amethyst crystals. A form called Brazilian twinning is particularly common in amethyst: in this type of twinning, regions of the quartz lattice grow in a mirror-image-like reverse orientation, manifesting as thin parallel bands or lines within the crystal ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ). When viewed under polarized light, these twinning bands can appear as different shades or shades of color. This internal structure, detectable in most natural amethysts, is one clue scientists use to distinguish synthetic from natural amethyst. Because laboratory-grown amethyst crystals are usually grown untwinned, they do not contain the distinct twinning bands found in natural stones ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ). Therefore, the presence of twinning patterns under a microscope can indicate the natural origin of an amethyst specimen.

Now, let's delve into the secret behind amethyst's striking purple color : This color arises from the very small amounts of impurities in its crystal structure and the radiation that acts on them. While quartz's chemical formula is SiO₂, in amethyst, the silicon atoms are replaced by trace amounts of iron atoms (typically a few ppm Fe). ( SciELO Brazil - Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation ) ( SciELO Brazil - Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation ) These iron atoms generally enter the quartz lattice in the +3 oxidation state (Fe³⁺), meaning that an additional positive charge must be balanced to electrically replace silicon (Si⁴⁺). In nature, this balancing is achieved by the presence of a small positive ion, such as lithium or sodium, in the crystal structure or by the formation of an "electron vacancy" (hole) ( Study on the effect of heat treatment on amethyst color and the cause of coloration | Scientific Reports ). The color of amethyst is related to this electron vacancy.

Natural amethyst often forms near rocks that contain traces of radioactive elements such as uranium and thorium. This increased environmental radiation affects some of the Fe³⁺ ions within the amethyst. In particular, low-level ionizing radiation emitted by the decay of potassium-40, uranium, and thorium naturally present in rocks strips electrons from Fe³⁺ ions within the quartz crystal, converting them to Fe⁴⁺ ( Amethyst | Museum of Radiation and Radioactivity ). As a result, the iron atom that replaced the Fe³⁺ loses an electron, gaining a +4 charge, and creating an electron vacancy (hole) in the crystal lattice. This combined structure, the color center shown as [FeO₄]⁰, is the source of amethyst's purple color ( Amethyst - Wikipedia ). In other words, the unit formed by the iron ion and the surrounding oxygens has become a center capable of absorbing light of a specific wavelength due to an electron deficiency.

These color centers absorb specific wavelengths of incident light. Spectroscopic analyses show that amethyst crystals have a distinct absorption band at approximately 545 nm in the visible absorption spectrum, corresponding to the charge transfer transition between iron ions and oxygen ( Study on the effect of heat treatment on amethyst color and the cause of coloration | Scientific Reports ). Because this wavelength corresponds to a greenish-yellow color, the light reflected from the amethyst due to its absorption is perceived as violet. As the density of iron-containing color centers increases, the amethyst color becomes darker purple (more "intense" or "saturated"). In short, the purple violet color of amethyst arises from the conversion of Fe³⁺ ions embedded in the crystal structure to the Fe⁴⁺ state under the influence of natural radiation, and the resulting defects absorbing certain light energies ( Amethyst | Museum of Radiation and Radioactivity ) ( Amethyst - Wikipedia ).

Scientists have also confirmed this mechanism through laboratory experiments. For example, a colorless quartz crystal was grown hydrothermally, iron was added to its structure, and then irradiated with gamma rays; the crystal turned purple and the iron transitioned from the Fe⁴⁺ state to the Fe⁴⁺ state. ( What Oxidation State of Iron Determines the Amethyst Color? | SpringerLink ). Advanced techniques such as Mössbauer spectroscopy have directly observed the presence of Fe⁴⁺ ions in the crystal after gamma irradiation, proving that the amethyst color is due to this valence change. ( What Oxidation State of Iron Determines the Amethyst Color? | SpringerLink ).

Amethyst's color is also sensitive to heating . At high temperatures (e.g., approximately 500°C and above), amethyst can lose its purple color or change to other colors. Scientific studies have shown that amethyst heated above 500°C turns yellow, transforming into a type of quartz called citrine ( Study on the effect of heat treatment on amethyst color and the cause of coloration | Scientific Reports ) . Between 420 and 440°C, amethyst's color centers are most unstable; at these temperatures, some amethyst specimens can turn green (praziolite). These color changes indicate that the Fe-based color centers dissolve or transform into a different form with heat. Indeed, the Fe⁴⁺ centers in amethyst are reduced back to Fe⁺⁺ or defects within the crystal are removed, thus eliminating the purple color. Similarly, it's known that amethyst stones exposed to strong UV light for extended periods can fade over time ( Amethyst gemstone information ). This purple hue is caused by the partial neutralization of color centers by high-energy rays. Therefore, storing highly valuable amethyst jewelry away from direct sunlight is recommended to preserve its color.

In short, amethyst's purple color and crystal structure are related to iron impurities and crystal defects at the atomic scale. This phenomenon, behind amethyst's beauty, is a fascinating scientific story at the intersection of geology and chemistry.

Amethyst Stone Benefits: Myths and Scientific Facts

Amethyst has been a stone to which humanity has attributed various meanings throughout history. Even its name derives from a benefit attributed to this stone in Ancient Greece: the word "Amethystos" means "not intoxicating" in Greek; for in Greek mythology, amethyst was believed to protect its owner from drunkenness ( Amethyst - Wikipedia ). Ancient Greeks and Romans crafted drinking glasses and coasters from amethyst to ward off the effects of intoxication. Today, amethyst and other crystals are popular in alternative medicine and New Age beliefs. Many metaphysical properties, such as reducing stress, absorbing negative energy, and providing mental calm and spiritual protection, are attributed to amethyst. But is there any scientific basis for these claims?

Modern scientific research has found no evidence that crystals have a direct therapeutic effect on human health or psychology. Scientists have not been able to provide data to support crystal therapy claims, which are based on the idea that illnesses are caused by the disruption of an imaginary "energy flow" in the body ( Crystal healing: Stone-cold facts about gemstone treatments | Live Science ). For example, there are no controlled clinical studies demonstrating that crystals with different chemical compositions or colors can cure specific physical ailments ( Crystal healing: Stone-cold facts about gemstone treatments | Live Science ). Therefore, the benefits of amethyst, such as stress relief, peace of mind, and energy clearing, cannot be scientifically explained beyond the placebo effect . According to a reliable health assessment cited by Healthline, there is no scientific evidence to support the rumors that amethyst provides mental and physical healing ( Amethyst Healing Properties and Uses in Alternative Medicine ). In other words, claims of amethyst's miraculous healing powers lack scientific basis , and crystal healing practices are largely dismissed as pseudoscience .

On the other hand, natural stones like amethyst can provide indirect psychological benefits. For example, the aesthetic beauty and sense of serenity evoked by purple amethyst crystals can help a person focus and relax during meditation. The decorative use of amethyst and similar crystals in spas and wellness centers can contribute to the relaxation of visitors by creating a pleasant and calming atmosphere. Indeed, the use of crystals in such settings can subjectively make some people feel good; however, this effect is thought to stem from the individual's psychological suggestions and beliefs rather than any specific energy of the crystal ( Crystal healing: Stone-cold facts about gemstone treatments | Live Science ). In other words, the relaxing effect attributed to amethyst is not scientifically measured as being related to any physical energy the stone emits, but rather to the positive emotions and expectations it evokes in the user.

The concrete and scientific benefits of amethyst, however, emerge more frequently in industrial and technological applications. As mentioned above, because amethyst is a type of quartz, it possesses a piezoelectric effect. This property allows quartz crystals to generate electric charges when an external mechanical stress is applied, or conversely, to vibrate and produce mechanical motion when an electric field is applied ( Amethyst - Wikipedia ). In technology, this principle is the basis of quartz oscillators . Many electronic devices, such as radio transmitters, sonar systems, and quartz watches, utilize quartz crystals as sources of constant-frequency vibration. Particularly in the mid-20th century, pure quartz crystals became a strategic material in radio and telecommunications. During World War II, tons of natural quartz crystals were collected from Brazil for use in oscillators that control radio frequencies; To meet this demand, programs to produce synthetic quartz in laboratory settings were initiated ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ) . By the 1950s, large, flawless quartz crystals were artificially produced by hydrothermal methods and began to be used in electronic circuits ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ). The internal structure of these crystals deliberately lacks the twinning defects found in amethyst because extremely precise and uniform vibrations are desired, especially in devices such as watches. Today, quartz crystals (natural or synthetic) serve as resonators or frequency control elements at the heart of many electronic devices, from watches to computers. ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ). Although the crystals used in these applications are typically colorless "rock crystal," amethyst has physical properties that could, in principle, serve the same purpose. For example, if an amethyst crystal is cut appropriately and integrated into an electronic circuit, it can power a watch by vibrating at a constant frequency of 32.768 Hz; its color does not affect this function.

In summary, the mystical benefits traditionally attributed to amethyst are not supported by scientific research. However, its aesthetic appeal as a gemstone and its natural beauty, which can positively impact human psychology, should not be overlooked. While science cannot demonstrate that amethyst cures physical ailments, understanding and using it holds value for humanity in various ways: it has provided cultural richness through its historical portrayal of legends and inspired industrial innovation.

Advanced Analysis Techniques, Laboratory Synthesis and Spectroscopy

Scientific studies on amethyst utilize a variety of advanced analytical techniques to understand the conditions surrounding the stone's formation and to reveal its structural and chemical intricacies. Furthermore, research focuses on the synthesis of high-quality amethyst crystals in the laboratory and the imitation and detailed study of natural amethyst.

Spectroscopic analyses: A number of spectroscopy methods are used to understand the structure and color of amethyst crystals. As mentioned above, UV-Vis spectroscopy reveals the absorption bands characteristic of amethyst's purple color. The primary absorption peaks, located around 360 nm, 545 nm, and 950 nm, are the signatures of Fe-bound color centers within the crystal ( Study on the effect of heat treatment on amethyst color and the cause of coloration | Scientific Reports ). The 545 nm band, in particular, is attributed to the charge transfer transition between the Fe³⁺ ion and the adjacent O²⁻ ion and is directly related to the saturation of amethyst's color ( Study on the effect of heat treatment on amethyst color and the cause of coloration | Scientific Reports ). Infrared (IR) spectroscopy is used to examine the presence of bound water or hydroxyl groups and trace elements within amethyst. IR analyses detected weak broad bands in the 3200–3600 cm⁻¹ region in natural amethyst samples and associated them with Al³⁺ or Fe³⁺ incorporation into the quartz structure ( SciELO Brazil - Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation ). For example, one study observed distinct differences in the IR spectra of amethysts with a high iron content; thanks to this, it was possible to distinguish iron and aluminum impurities in the amethyst ( SciELO Brazil - Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation ). Electron paramagnetic resonance (EPR) spectroscopy is also a technique used to detect paramagnetic (unpaired electron) centers in amethyst. EPR captures the signals of centers responsible for amethyst color (e.g., O⁻ radicals or Fe⁴⁺–O⁻ pairs), allowing the presence and dynamics of these centers to be studied. Similarly, Mössbauer spectroscopy has been used to distinguish between the different oxidation states of iron ions. Mössbauer analyses have clearly demonstrated that Fe⁴⁺ ions in amethyst samples are transformed into Fe⁴⁺ after gamma irradiation ( What Oxidation State of Iron Determines the Amethyst Color? | SpringerLink ). The combined use of these advanced techniques provides comprehensive confirmation of the origin of amethyst color.

Structural and chemical analyses: When amethyst, and quartz in general, is examined using X-ray diffraction (XRD), its atomic arrangement is observed to be periodic and regular. There is no difference in XRD patterns between natural amethyst and colorless quartz; in other words, the crystal structure of amethyst is essentially the same as quartz. However, lattice parameters of amethyst crystals have been examined using XRD at different temperatures. A 2020 study reported that heating amethyst did not significantly change the crystal lattice dimensions, but the crystallinity index (i.e., the degree of regularity) decreased at higher temperatures ( Study on the effect of heat treatment on amethyst color and the cause of coloration | Scientific Reports ). This suggests that the loss of amethyst's color is not due to the disruption of the crystal structure, but rather to the disappearance of defects (color centers) within the lattice. In other words, the basic structure of the crystal is preserved, while the color-imparting centers are eliminated by heat.

Fluid inclusion analysis is also an important method for understanding the conditions during amethyst formation. Tiny pockets of fluid trapped within the crystal provide information about the composition and temperature of the fluid from which the amethyst formed. Melting-boiling tests of these microscopic fluids can be performed to determine the conditions (e.g., salinity and temperature) under which the amethyst grew. As previously mentioned, a fluid inclusion study on an amethyst vein in Canada showed that amethyst crystals formed at temperatures as low as approximately 75°C ( Amethyst from Newfoundland, Canada: Geology, Internal Features , and Fluid Inclusion Microthermometry). This type of analysis plays a critical role in understanding the geothermal evolution of amethyst deposits.

Laboratory synthesis and synthetic amethyst: Producing amethyst crystals in a laboratory, which takes millions of years to form in nature, in a shorter time is of interest from both industrial and scientific perspectives. Hydrothermal synthesis of quartz has been attempted since the late 19th century, but its practical development was achieved after World War II ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ). Colorless quartz crystals, grown in high-pressure vessels (autoclaves) by feeding silica and maintaining the appropriate temperature gradient, are now routinely obtained in industry. The only step required to obtain amethyst from these colorless synthetic quartz crystals is to dope the crystal with iron (mixing a small amount of iron salt into the feed material) and then expose it to irradiation . Indeed, in the second half of the 20th century, synthetic amethyst production began on a commercial scale in the Soviet Union and Japan ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ). Since approximately the 1970s, iron-doped quartz grown using hydrothermal methods has been transformed to purple by controlled gamma irradiation and marketed as laboratory-made amethyst ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ). While these synthetic amethysts are generally used for jewelry, they can appear very similar to natural amethysts. However, subtle clues, such as the twinning structure mentioned above, can reveal their laboratory origin. Expert gemologists can detect the absence of twinning bands by examining synthetic amethysts under a polarizing microscope, as most synthetic amethysts are single crystals (untwinned). Synthetic and natural amethysts can also be distinguished by chemical trace element analysis ; natural amethysts often contain not only iron but also other elements such as aluminum, while synthetics may have purer formulas for control purposes. For example, a scientific study found that the Al content in natural amethysts is significantly higher (generally >120 ppm) while that in synthetics is much lower ( SciELO Brazil - Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation ). Thanks to all these advanced analysis techniques, the risk of selling synthetic amethysts as natural in the jewelry market can be largely prevented by scientific testing.

Conclusion: The scientific journey of amethyst reveals how intriguing a natural phenomenon it is, beyond its mere aesthetic value. Geologists and mineralogists have been conducting studies for decades to understand the formation conditions of amethyst, the cause of its purple color, and its differences from other quartz varieties. These studies occur at the intersection of disciplines such as crystal chemistry, geochemistry, mineral physics, and materials science. The findings not only illuminate the truth behind amethyst's beauty but also provide general information on crystal defects, color centers, and material synthesis. Amethyst continues to captivate hearts as an ornamental stone that has inspired legends for centuries, while also retaining its scientific significance as a natural wonder that guides us in understanding the world of crystals.

Sources:

1. Amethyst – Wikipedia : General information about the definition of amethyst stone, its chemical structure and the formation of its purple color ( Amethyst - Wikipedia ) ( Amethyst | Museum of Radiation and Radioactivity ).

2. Lameiras et al. (2009) – Materials Research : Infrared and chemical characterization of natural amethyst and praziolite samples; Analysis of Fe contents and color centers in amethyst ( SciELO Brazil - Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation ) ( SciELO Brazil - Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation and prasiolites colored by irradiation ).

3. Rossman (1994) – Rev. in Mineralogy, Vol. 29 : Review of the colored varieties of silica minerals; study of iron inclusions and color formation in amethyst.

4. Scientific Reports (2020) – Nature : Color change of amethyst upon heating and UV-Vis spectroscopy results; showing that the 545 nm band is due to Fe³⁺–O²⁻ charge transfer ( Study on the effect of heat treatment on amethyst color and the cause of coloration | Scientific Reports ).

5. ORAU – Museum of Radiation and Radioactivity : Explanation on the effect of radiation on the color of amethyst; natural radiation oxidizes Fe³⁺ to Fe⁴⁺, creating the purple color ( Amethyst | Museum of Radiation and Radioactivity ).

6. GIA – Gems & Gemology, Fall 1986 : Methods for the separation of natural and synthetic amethyst based on twinning; commercial production and historical development of synthetic amethyst ( A Simple Procedure to Separate Natural from Synthetic Amethyst on the Basis of Twinning ) .

7. Live Science (2022) – Jonathan Gordon, Elizabeth Peterson : Scientific assessment of crystal therapy claims; lack of evidence that crystals heal ( Crystal healing: Stone-cold facts about gemstone treatments | Live Science ) .

8. Healthline (2020) – Emily Cronkleton : Review of the claimed benefits of amethyst in alternative medicine; highlighting the lack of scientific evidence supporting these claims ( Amethyst Healing Properties and Uses in Alternative Medicine ).

9. Geology Science: Amethyst Properties & Formation : General information about the physical properties of amethyst (hardness, density, refractive index, etc.) and formation theories ( Amethyst | Properties, Formation, Gemstone » Geology Science ) ( Amethyst | Properties, Formation, Gemstone » Geology Science ).

10. Mindat/Gemdat – Amethyst Gemstone Information : Reference table for the gemological values ​​(RI, SG, pleochroism, color reasons) and typical environments of amethyst ( Amethyst gemstone information ) .