Hubbry Logo
FacetFacetMain
Open search
Facet
Community hub
Facet
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Facet
Facet
Facet
View on Wikipedia
from Wikipedia
A faceted amethyst

Facets (/ˈfæsɪt/) are flat faces on geometric shapes. The organization of naturally occurring facets was key to early developments in crystallography, since they reflect the underlying symmetry of the crystal structure. Gemstones commonly have facets cut into them in order to improve their appearance by allowing them to reflect light. The earliest diamond cutting techniques were simply to polish the natural shape of rough diamonds, often octahedral crystals. It wasn't until the 14th century that faceting, the process of cutting and polishing a gemstone to create multiple flat surfaces or facets, was first developed in Europe.[1]

Facet arrangements

[edit]
A 19th century tiara with blue sapphires and diamonds, cut in old European style.

Of the hundreds of facet arrangements that have been used, the most famous is probably the round brilliant cut, used for diamond and many colored gemstones. This first early version of what would become the modern Brilliant Cut is said to have been devised by an Italian named Peruzzi, sometime in the late 17th century.[2][3] Later on, the first angles for an "ideal" cut diamond were calculated by Marcel Tolkowsky in 1919. Slight modifications have been made since then, but angles for "ideal" cut diamonds are still similar to Tolkowsky's formula. Round brilliants cut before the advent of "ideal" angles are often referred to as "Early round brilliant cut" or "Old European brilliant cut" and are considered poorly cut by today's standards, though there is still interest in them from collectors. Other historic diamond cuts include the "Old Mine Cut" which is similar to early versions of the round brilliant, but has a rectangular outline, and the "Rose Cut" which is a simple cut consisting of a flat, polished back, and varying numbers of angled facets on the crown, producing a faceted dome. Sometimes a 58th facet, called a culet is cut on the bottom of the stone to help prevent chipping of the pavilion point. Earlier brilliant cuts often have very large culets, while modern brilliant cut diamonds generally lack the culet facet, or it may be present in minute size.

Cutting facets

[edit]
Cutting and polishing diamonds in the Netherlands, 1946.

The art of cutting a gem is an exacting procedure performed on a faceting machine. The ideal product of facet cutting is a gemstone that displays a pleasing balance of internal reflections of light known as brilliance, strong and colorful dispersion which is commonly referred to as "fire", and brightly colored flashes of reflected light known as scintillation. Typically transparent to translucent stones are faceted, although opaque materials may occasionally be faceted as the luster of the gem will produce appealing reflections. Pleonaste (black spinel) and black diamond are examples of opaque faceted gemstones.

Facet angles

[edit]

The angles used for each facet play a crucial role in the outcome of a gem. While the general facet arrangement of a particular gemstone cut may appear the same in any given gem material, the angles of each facet must be carefully adjusted to maximize the optical performance. The angles used will vary based on the refractive index of the gem material. When light passes through a gemstone and strikes a polished facet, the minimum angle possible for the facet to reflect the light back into the gemstone is called the critical angle.[4] If the ray of light strikes a surface lower than this angle, it will leave the gem material instead of reflecting through the gem as brilliance. These lost light rays are sometimes referred to as "light leakage", and the effect caused by it is called "windowing" as the area will appear transparent and without brilliance. This is especially common in poorly cut commercial gemstones. Gemstones with higher refractive indexes generally make more desirable gemstones, the critical angle decreases as refractive indices increase, allowing for greater internal reflections as the light is less likely to escape.

The faceting machine

[edit]
An amethyst on a dop stick in a faceting machine

This machine uses a motor-driven plate to hold a precisely flat disk (known as a "lap") for the purpose of cutting or polishing. Diamond abrasives bonded to metal or resin are typically used for cutting laps, and a wide variety of materials are used for polishing laps in conjunction with either very fine diamond powder or oxide-based polishes. Water is typically used for cutting, while either oil or water is used for the polishing process.

The machine uses a system generally called a "mast" which consists of an angle readout, height adjustment and typically a gear (called an "index gear") with a particular number of teeth is used as a means of setting the rotational angle. The angles of rotation are evenly divided by the number of teeth present on the gear, though many machines include additional means of adjusting the rotational angle in finer increments, often called a "cheater". The stone is bonded to a (typically metal) rod known as a "dop" or "dop stick" and is held in place by part of the mast referred to as the "quill".

The modern faceting process

[edit]
Moving an amethyst from one dop stick to another using a transfer jig.

The dopped stone is ground at precise angles and indexes on cutting laps of progressively finer grit, and then the process is repeated a final time to polish each facet. Accurate repetition of angles in the cutting and polishing process is aided by the angle readout and index gear. The physical process of polishing is a subject of debate. One commonly accepted theory is that the fine abrasive particles of a polishing compound produce abrasions smaller than the wavelengths of light, thus making the minute scratches invisible. Since gemstones have two sides (the crown and pavilion), a device often called a "transfer jig" is used to flip the stone so that each side may be cut and polished.[4]

Other methods

[edit]
Joseph Asscher cleaving the Cullinan diamond using a steel wedge-like blade and a small club.

Cleaving relies on planar weaknesses of the chemical bonds in the crystal structure of a mineral. If a sharp blow is applied at the correct angle, the stone may split cleanly apart. While cleaving is sometimes used to split uncut gemstones into smaller pieces, it is never used to produce facets. Cleaving of diamonds was once common, but as the risk of damaging a stone is too high, undesirable diamond pieces often resulted. The preferred method of splitting diamonds into smaller pieces is now sawing.[3]

An older and more primitive style of faceting machine called a jamb peg machine used wooden dop sticks of precise length and a "mast" system consisting of a plate with holes carefully placed in it. By placing the back end of the dop into one of the many holes, the stone could be introduced to the lap at precise angles. These machines took considerable skill to operate effectively.[4]

Another method of facet cutting involves the use of cylinders to produce curved, concave facets. This technique can produce many unusual and artistic variations of the traditional faceting process.

Natural faceting

[edit]

Many crystals naturally grow in faceted shapes. For instance, common table salt forms cubes and quartz forms hexagonal prisms. These characteristic shapes are a consequence of the crystal structure of the material and the surface energy, as well as the general conditions under which the crystal formed.

A variety of quartz, known as Herkimer diamonds due to their well-formed natural facets and clear quality.

The Bravais lattice of the crystal structure defines a set of possible "low-energy planes", which are usually planes on which the atoms are close-packed. For instance, a cubic crystal may have low-energy planes on the faces of the cube or on the diagonals. The planes are low-energy in the sense that if the crystal is cleaved along these planes, there will be relatively few broken bonds and a relatively small increase in energy over the unbroken crystal. Equivalently, these planes have a low surface energy. The planes with the lowest energy will form the largest facets, in order to minimize the overall thermodynamic free energy of the crystal. If the surface energy as a function of the planes is known, the equilibrium shape of the crystal may be found via the Wulff construction.

Growth conditions, including the surface the crystal is growing on top of (the substrate), may change the expected shape of the crystal; for instance, if the base of the crystal is under stress from the substrate, this may favor the crystal growing taller rather than growing outwards along the substrate. The surface energy, including the relative energies of the different planes, depend on many factors including the temperature, the composition of the surroundings (e.g. humidity), and the pressure.

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Facet

View on Grokipedia
from Grokipedia
A facet is a small, flat, polished surface, typically one of many forming a geometric figure such as the faces of a cut , , or . In , it denotes a smooth, planar area on a or , often resulting from natural formation or wear, as seen in the facet joints of the spine that facilitate movement between vertebrae. Figuratively, the term describes one distinct aspect, phase, or element of a multifaceted subject, problem, or personality. In , refers to the precise cutting and process that shapes rough stones into brilliant gems by creating symmetrical, angular surfaces to optimize reflection, , and dispersion. This technique, dating back centuries, transforms opaque or dull materials into sparkling jewels, with common styles including the round brilliant cut featuring 58 facets for maximum and scintillation. The geometric arrangement of facets—divided into , , and sections—directly influences a gem's optical performance and perceived value. In and , a facet is a bounding plane of a or lattice, where the organization of naturally occurring facets played a pivotal role in early studies of and . Extending to higher dimensions, facets represent the maximal faces of polytopes, essential in combinatorial for analyzing shapes and their properties. In , faceted classification employs multiple independent semantic categories—or facets—such as form, subject, or time, to systematically organize knowledge or data, enabling flexible searching and navigation beyond rigid hierarchies. Pioneered in and archival systems, this approach allows users to combine attributes dynamically, improving retrieval in digital collections and databases.

Fundamentals of Facets

Definition and Purpose

A facet is a small, flat, polished surface on a cut or , precisely angled and arranged to maximize the interaction of through reflection, , and dispersion. The primary purpose of facets is to enhance the visual appeal of by improving brilliance—the return of white to the observer's eye—, which is the dispersion of into spectral colors, and scintillation, the dynamic sparkle produced by flashes during movement. Pavilion facets primarily reflect upward to boost brilliance and contribute to , while crown facets refract incoming to facilitate dispersion and for scintillation. This optical optimization transforms rough material into highly desirable jewels, increasing their aesthetic and economic value compared to simpler cuts. For transparent gemstones suitable for faceting, such cuts often command higher prices than cabochons due to the intensive labor, skill, and time required for precise angle control and polishing, often resulting in significantly greater resale value for well-cut stones. Key terminology in faceted gemstones includes the crown, the upper portion above the girdle containing facets that gather and bend light; the pavilion, the lower portion below the girdle with facets that reflect light back through the crown; the girdle, the equatorial edge separating the crown and pavilion that defines the stone's outline; the culet, a small facet or point at the pavilion's base to prevent chipping; and the table, the largest flat facet on the crown that serves as the primary window for light entry.

Optical Principles

Facets in gemstones manipulate light through fundamental optical phenomena, including , reflection, and dispersion, to enhance visual appeal. Refraction occurs when light passes from air (refractive index approximately 1) into the , bending according to : n1sin⁡θ1=n2sin⁡θ2n_1 \sin \theta_1 = n_2 \sin \theta_2, where nn is the and θ\theta the angle of incidence or . This bending directs light deeper into the stone, where it can interact with internal facets. Reflection, particularly (TIR), happens when light strikes a facet at an angle greater than the critical angle, preventing escape and redirecting it back toward the viewer. Dispersion arises because the varies slightly with , causing white light to split into spectral colors as it refracts through the gem. These principles produce key visual effects in faceted gems. Brilliance results from the efficient return of white through multiple reflections between the (upper) and (lower) facets, creating intense brightness. , or the display of rainbow flashes, stems from dispersion concentrated in triangular or kite-shaped facets, where separates into colors upon entering or exiting. Scintillation refers to the sparkling play of and dark areas as the gem moves, caused by facet edges alternately catching and releasing rays. The profoundly influences facet design, as higher values enable greater light bending and retention. For example, has a of 2.42, allowing for dramatic brilliance, while sapphire's index of 1.77 produces a softer sparkle, necessitating adjusted facet angles to optimize performance. The critical angle, calculated as θc=arcsin⁡(1/n)\theta_c = \arcsin(1/n), determines the threshold for TIR; for , it is approximately 24.4°, meaning pavilion facets must exceed this by a safety margin (typically 34-35°) to prevent light leakage through the base. In high-index materials like , precise angles are essential to maximize TIR and avoid dullness from escaped light.

Facet Designs

Standard Arrangements

Standardized facet arrangements in gem cutting refer to established patterns that prioritize efficiency, , and optimal light interaction, particularly for and other transparent gems. These patterns emerged from historical refinements aimed at maximizing brilliance while adhering to industry benchmarks for proportions and facet counts. Organizations such as the (GIA) and the American Gem Society (AGS) define standards for and proportions to ensure consistent quality across cuts. The round brilliant cut represents the most iconic standard arrangement, featuring 58 facets—33 on the and 25 on the —designed to achieve maximum light return through precise angles that promote . Ideal proportions for this cut include a table size of approximately 53% of the and a total depth of 59.5%, which balance brilliance and fire. The AGS specifies angles of 34.5° and angles of 40.75° for optimal performance in round brilliants, ensuring predictable scintillation and minimizing light leakage. Other common standards include the , a rectangular modified brilliant typically with 76 facets (though variations can range from 50 to over 76) that delivers intense sparkle while maintaining a square outline with pointed corners. The emerald cut employs a step-cut design with rectangular facets arranged in concentric rows, emphasizing the gem's clarity and subtle elegance rather than fiery dispersion, typically featuring around 50-58 facets. The marquise cut, an elongated oval with pointed ends and 58 facets, creates an illusion of greater length and size, enhancing the wearer's finger appearance through its boat-like symmetry. Facet counts and proportions may vary slightly depending on specific implementations and gem material. These standardized patterns offer advantages in production and performance, as their fixed facet counts and proportions allow for repeatable light behavior, facilitating quality control in manufacturing and reliable optical outcomes. By adhering to GIA and AGS guidelines, cutters achieve symmetry that ensures even light distribution, reducing variability and enhancing market value through verified consistency.

Advanced and Custom Patterns

Advanced and custom facet patterns deviate from standardized configurations to achieve artistic expressions, symbolic motifs, or optimized performance tailored to specific materials. These designs often involve intricate and non-uniform facet arrangements that prioritize visual impact over efficiency, allowing cutters to enhance unique properties like color or symbolic patterning. While building on principles of light return seen in standard arrangements, such patterns demand precise control to maintain optical integrity. Facet counts and proportions may vary slightly depending on specific implementations and material. Fantasy cuts represent a subset of advanced designs that create symbolic or visually striking internal patterns through exact facet alignment. The Hearts and Arrows cut, applied primarily to round brilliant diamonds, achieves eight symmetrical "arrows" on and eight "hearts" in the when viewed through specialized scopes, resulting from overlapping facet reflections in highly symmetrical stones. This pattern symbolizes love and precision, requiring tolerances as tight as 0.1 degrees in facet angles to avoid distortion. Similarly, star cuts produce radiating star motifs, such as an 8-point star, by adjusting angles to 40-42 degrees and aligning lower facets to form pointed intersections that reflect light into geometric bursts. These fantasy elements elevate the gem's aesthetic appeal beyond mere brilliance, often at the expense of yield from rough material. Custom designs further exemplify tailored faceting for material optimization. The Portuguese cut features a large table facet—up to 70% of the width—and a high crown rising to 20-25 degrees, which maximizes by increasing dispersion in the upper portion while maintaining a deep for brightness. In contrast, the Barion cut features a step-cut crown and a modified brilliant-cut pavilion, enhancing color saturation in fancy colored gems like or by concentrating paths to deepen perceived hue without excessive darkening. For opals, concave facets introduce subtle curvature to the pavilion, promoting even diffusion across play-of-color layers and reducing harsh reflections that could disrupt . Faceting considerations for colored stones emphasize adapting pattern complexity to the material's inherent hue. Unlike colorless gems, where numerous small facets maximize scintillation, colored stones benefit from fewer, larger facets—typically 30-50 total—to preserve and amplify color uniformity, as excessive subdivision can dilute saturation by light inefficiently. The Asscher cut illustrates this approach, employing a square outline with cropped corners and step-like facets to create a "hall of mirrors" effect that highlights tone in gems like emerald or , balancing geometric elegance with color enhancement. Implementing advanced and custom patterns presents notable challenges, including the elevated skill required for non-standard angles and symmetries, which can extend cutting time by 50-100% compared to routine work. Deviations from ideal proportions risk reduced brilliance, as misaligned facets may cause leakage or uneven scintillation, potentially lowering the gem's overall value despite artistic intent.

Faceting Techniques

Historical Development

The practice of faceting gemstones originated in ancient civilizations, where basic shaping techniques laid the groundwork for more sophisticated methods. In around 2000 BCE, artisans employed simple flat laps and to polish and shape hard stone beads, often using tools combined with or emery for smoothing surfaces. This early work focused on functional adornments rather than optical enhancement. The and Romans advanced these techniques by incorporating hand tools, such as drills and wheels, to achieve greater in engraved gems like intaglios and cameos, utilizing emery as a key abrasive for precision. Medieval innovations marked a shift toward more deliberate cutting, particularly for diamonds, influenced by cultural exchanges. In from the 6th century CE, lapidaries began grinding diamonds into powder for polishing other gems, with early texts like the Ratnapariksa describing rudimentary shaping methods that hinted at faceted forms. By the 9th to 11th centuries, Islamic artisans in and developed polyhedral faceting techniques, producing simple table cuts evident in jewelry artifacts. In during the , cutters in and popularized the rose cut—a hemispherical arrangement of triangular facets on a flat base—and the table cut, which featured a large central facet to improve light reflection and play. Key 15th- to 17th-century milestones accelerated the evolution of faceting through technological and artistic advancements. In 1476, Flemish polisher Lodewyk van Bercken invented the scaif, a spinning wooden wheel coated with , enabling faster and more uniform polishing of facets and establishing absolute symmetry as a standard. This innovation facilitated the creation of more complex designs. By the 1660s, Cardinal Jules Mazarin commissioned the Mazarin cut, an early brilliant-style diamond with 17 facets on the crown and 17 on the pavilion, optimizing light return in cushion-shaped stones. The 18th and 19th centuries saw further refinements and the onset of , exemplified by large-scale projects like the of diamond in 1908. Weighing 3,106 carats in rough form, the Cullinan was cleaved and faceted by Asscher in over several months, yielding nine major stones including the 530-carat Great Star of Africa, demonstrating the precision achievable with emerging powered tools. The transition to began in the 1800s, as Antwerp's cutting houses adopted steam-powered bruting machines (patented in 1874) and wheels, shifting from labor-intensive hand-lapping to efficient powered operations that increased production scale.

Modern Processes and Tools

Modern faceting processes rely on precision-engineered machines that enable lapidaries to cut and polish gemstones with high accuracy, typically achieving tolerances within 0.1 degrees for facet angles. These machines, such as the Ultra Tec V5 or Facetron models, incorporate mechanical and digital controls to automate repetitive tasks while allowing manual adjustments for custom work. Developed in the late and refined through the 21st, they represent a shift from manual scaifes to motorized systems, improving consistency and reducing waste in gem production. As of 2025, AI-driven software optimizes facet angles for specific rough stones, improving yield and light performance. Key components of a standard faceting include the mast, which serves as the vertical support for the dop holder that secures the ; the , an adjustable arm that precisely sets the cutting angle; the index gear, which controls the rotational spacing between facets (often using 96-tooth gears for standard round brilliants); and the , a rotating impregnated with particles or other abrasives for cutting and polishing. Digital versions integrate computer controls, such as encoders for angle measurement and automated height adjustments via CNC platforms, allowing for programmable sequences in high-volume settings. systems are standard to prevent overheating and cracking of the gem material during operation. The faceting process begins with doping, where the rough gemstone is cleaned, inspected for inclusions, and attached to a metal dop stick using high-temperature wax or glue, then inserted into the machine's holder. Preforming follows, using a coarse lap (e.g., 260-grit diamond) to roughly shape the stone to the desired outline, removing excess material while establishing the basic girdle diameter. Faceting proper involves cutting the pavilion facets first—starting with the main pavilion facets at angles around 40.75° for diamonds—followed by lower girdle facets, the girdle at 90°, crown mains at 34.5° to 35°, star facets, upper girdle facets, and finally the table, set parallel to the girdle (approximately 0° relative to the girdle plane). Each facet is cut sequentially by adjusting the quill angle and indexing the gear to ensure even spacing, with protractors or digital readouts verifying precision to within 0.1°. Polishing concludes the process, employing fine laps (e.g., 1,500-grit or ceramic-embedded) at lower speeds to achieve a mirror finish, often starting with break facets before mains and the table to minimize scratches. In industrial setups, automated transfer devices move the dop between machines for bruting and stages, enhancing efficiency; a small gem (under 1 carat) may take 6-8 hours total, while larger stones can require days. protocols include protective , dust extraction, and stable machine mounting to mitigate risks from high-speed laps and particles.

Alternative Methods

Hand faceting involves manually shaping and stones using tools such as laps, files, and dop sticks, without relying on automated machines. The is attached to a dop stick and swept across laps with hand pressure to create uniform facets, often guided by auditory cues like the shift from grinding sounds to a smoother "shhh" during . This method is particularly suited for custom work, repairs—such as recutting over-cut facets on bi-color opals—and applications in regions with limited access to advanced equipment, though it is labor-intensive and time-consuming compared to machine-based processes. Laser cutting represents an emerging alternative for precision preforming and intricate patterning in gemstones, especially and synthetics, by directing a high-powered beam through a thin jet to achieve clean, taper-free cuts. Systems like Synova's MicroJet enable accuracy down to 3-5 microns, minimizing heat damage, micro-cracks, and material waste—potentially increasing yield from rough by up to 20% in CVD slicing—while allowing for complex designs that enhance performance. cutting complements this for initial shaping of hard materials like , using high-pressure mixed with abrasives such as to slice through up to 12 inches of stone without thermal alteration, reducing waste in preforming stages before traditional . For soft or fragile materials like , adaptations often incorporate or protective techniques to avoid cracking, though opals' sensitivity to heat and chemicals limits direct ; instead, gentle mechanical with on felt pads is preferred, sometimes combined with experimental concave effects achieved via specialized mandrels rather than acids. , while primarily used to deposit metal layers onto faceted gems for jewelry settings, can indirectly support soft stones by stabilizing them during handling, as seen in workflows sealing opals with conductive paints before deposition to prevent or damage. Adaptations for non-gem materials, such as or , require modified tools to address unique challenges like or inclusions. like or tektites (formed from impacts) can be faceted using diamond laps, but bubbles and hazy polishing demand careful preforming to avoid surface breaks, yielding stones with subdued sparkle. from are faceted into small gems (typically 0.10-0.30 ct) after slab sawing, with challenges including variable and drab hues, while iron meteorites often use grinding wheels for etching-like surface effects rather than true facets due to their metallic composition. Quartz-like in these materials necessitates reduced pressure and frequent angle checks to prevent chipping.

Natural Faceting

Geological Formation

Natural facets in minerals form primarily through the orderly growth of crystals in unconstrained environments, where atoms arrange into a repetitive lattice structure that manifests as flat, planar faces on the crystal surfaces. This process occurs when mineral nuclei develop into larger crystals without interference from surrounding materials, allowing the external expression of the internal atomic symmetry; for instance, in open cavities such as geodes, silica-rich solutions precipitate quartz crystals that project inward with well-defined faces. Additionally, fracturing of crystals can expose cleavage planes—weak structural zones aligned with the lattice—that mimic natural facets by creating smooth, flat surfaces parallel to potential growth faces. Key geological processes driving facet formation include hydrothermal activity and metamorphic pressures. In hydrothermal systems, hot, mineral-laden fluids circulate through fractures in rocks, cooling and depositing crystals with inherent faceted terminations; points, for example, commonly form this way in veins as silica precipitates from supersaturated solutions under elevated temperatures and s. Metamorphic processes, involving intense and pressure without , recrystallize minerals and align atomic planes, promoting the development of faceted crystals like porphyroblasts in deformed rocks. The shape and orientation of these facets are governed by the mineral's inherent crystal , which dictates the possible forms through repeating atomic patterns. Cubic in minerals like results in dodecahedral crystals with twelve rhombic faces, while hexagonal in beryl produces prismatic forms with six-sided terminations. , where adjacent crystal domains share a lattice but orient differently across a twin plane, can create pseudo-facets by producing reentrant angles or flattened surfaces that resemble additional growth faces. The scale of natural facets varies widely, from microscopic to macroscopic, influenced by growth conditions and availability of space. In drusy , numerous tiny crystals—often millimeters or less in size—coat cavity walls in dense clusters, forming a sparkling layer of micro-facets that is relatively common in geodes. In contrast, crystals in pockets can develop large, well-faceted prisms up to decimeters long, though such sizable, euhedral examples are rarer due to the need for prolonged, undisturbed growth in volatile-rich environments.

Notable Natural Examples

One of the most iconic examples of natural faceting is found in diamonds, which commonly form as octahedral crystals featuring eight triangular facets. These facets arise from the cubic crystal lattice of carbon atoms arranged in a tetrahedral structure, stabilized under extreme pressures of approximately 5-6 gigapascals and temperatures around 900-1300°C deep within the Earth's mantle. Quartz varieties also exhibit striking natural , particularly Herkimer diamonds from , which are double-terminated quartz crystals with six pyramidal facets on each termination, giving them a diamond-like appearance due to their clarity and geometric precision. These formations result from silica-rich fluids filling cavities in dolomitic , allowing free growth on all sides without attachment to a matrix. points, another quartz variant, display similar natural terminations with pyramidal facets atop hexagonal prisms, often tinted brown by natural irradiation, and are prized for their elongated, pointed habits in hydrothermal vein deposits. Among other gems, fluorite forms octahedrons through its perfect octahedral cleavage, which creates eight triangular faces that mimic faceted surfaces, though these are planes of weakness rather than growth faces, often resulting in vibrant, translucent purple or green crystals from hydrothermal deposits. Pyrite, known as fool's gold, produces cubic crystals with six square facets derived from its isometric iron-sulfide structure, where iron atoms are bonded to disulfide groups (S₂), yielding a metallic luster and striated faces in sedimentary or metamorphic environments. Natural faceted crystals hold significant collectible value due to their rarity and unaltered state, often displayed as specimens in museums such as the Smithsonian National Museum of Natural History, where they exemplify geological artistry without human intervention. Unlike cut gems, these natural examples lack polish, retaining matte or etched surfaces and visible inclusions like fluid pockets or growth lines, which enhance their scientific and aesthetic appeal for collectors focused on mineral habits and formations.

References

  1. https://www.merriam-webster.com/dictionary/facet
  2. https://dictionary.cambridge.org/us/dictionary/english/facet
  3. https://www.dictionary.com/browse/facet
  4. https://www.gemsociety.org/article/gemstone-facets/
  5. https://www.gia.edu/gia-news-research-value-factors-gem-cutting-styles-definitions
  6. https://www.gemsociety.org/article/the-role-of-faceting-in-gemology/
  7. https://www.collinsdictionary.com/us/dictionary/english/facet
  8. https://www.sciencedirect.com/topics/computer-science/faceted-classification
  9. https://dictionary.archivists.org/entry/faceted-classification.html
  10. https://www.gia.edu/diamond-cut/diamond-cut-anatomy-round-brilliant
  11. https://www.gia.edu/gems-gemology/Optimizing-Face-Up-Appearance-in-Colored-Gemstone-Faceting
  12. https://www.gemsociety.org/article/gem-cutting-terms/
  13. https://www.gemsociety.org/article/measuring-gemstone-ri-1-81/
  14. https://www.ganoksin.com/article/basic-optical-principles-gemology/
  15. https://www.gemsociety.org/article/table-refractive-index-double-refraction-gems/
  16. https://usfacetersguild.org/refractive-index-and-critical-angle/
  17. https://www.gia.edu/gia-about/4cs-cut
  18. https://members.americangemsociety.org/page/performancebasedcut
  19. https://www.leibish.com/blogs/diamonds/facets-of-a-round-diamond
  20. https://www.onlinediamondbuyingadvice.com/diamond-education/diamond-cut/
  21. https://beyond4cs.com/shapes/round/ideal-proportions/
  22. https://www.withclarity.com/blogs/diamond/princess-cut-diamonds
  23. https://www.whiteflash.com/diamond-education/diamond-shapes/emerald-cut/
  24. https://taylorandhart.com/us/diamond-guidance/diamond-shapes/marquise
  25. https://www.igi.org/what-are-hearts-arrows-diamonds/
  26. https://www.gemsociety.org/article/overview-of-gem-cutting-styles/
  27. https://www.gemselect.com/other-gems/portuguese-cut-gemstones.php
  28. https://www.gemsociety.org/article/barion-concept-cut-design/
  29. https://www.gia.edu/doc/Value-Factors-Design-Cut-Quality-Colored-Gemstones-Gem-Market-News-GIA.pdf
  30. https://4cs.gia.edu/en-us/blog/guide-diamond-shapes-engagement-rings/
  31. https://www.gia.edu/gia-news-research-colored-stone-cut-quality-what-to-look-for
  32. https://www.gemsociety.org/article/lapidary-technology-history-laps-and-polish/
  33. https://www.gemsociety.org/article/the-history-of-lapidary/
  34. https://www.naturaldiamonds.com/historic-diamonds/diamond-cutting-history/
  35. https://www.langantiques.com/university/a-history-of-diamond-cutting/
  36. https://royalasscher.com/blogs/royal-asscher-blog/the-cullinan-diamond
  37. https://thenorthwaystudio.com/blogs/news/cut-by-time-a-history-of-gemstone-shapes-technology-and-jewelry-trends
  38. https://www.gemsociety.org/article/story-gemstone-faceting-equipment/
  39. https://www.ultratec-facet.com/product/v5-digital/
  40. https://www.gia.edu/doc/Modern-Diamond-Cutting-and-Polishing.pdf
  41. https://www.gemsociety.org/article/faceting-made-easy-part-2-faceting-machines-equipment/
  42. https://www.gemsociety.org/article/digital-faceting-machine/
  43. https://www.gemsociety.org/article/lapidary-fundamentals-gemstone-faceting/
  44. https://www.synova.ch/products/diamond-cutting-systems/item/140-davinci-diamond-factory.html
  45. https://www.headwaterjet.net/can-a-water-jet-cut-through-a-diamond.html
  46. https://www.techniwaterjet.com/water-jet-stone-cutting/
  47. https://opalgalaxy.com/opal-polishing-101/
  48. https://www.ultratec-facet.com/concave-faceting-gemstones/
  49. https://www.basketofblue.com/electroforming-tutorial/
  50. https://www.gemsociety.org/article/natural-glass/
  51. https://www.attawaygems.com/NMFG/Faceting_Pallasite_Peridot.html
  52. https://www.meteorite-times.com/tools-and-techniques-for-cutting-and-finishing-meteorites/
  53. https://opengeology.org/Mineralogy/4-crystals-and-crystallization/
  54. https://naturalhistory.si.edu/education/teaching-resources/earth-science/gems-and-minerals-beauties-and-building-blocks
  55. https://opengeology.org/Mineralogy/3-properties/
  56. https://www.gia.edu/gems-gemology/winter-2022-colored-stones-unearthed
  57. https://geo.libretexts.org/Bookshelves/Geology/Mineralogy_(Perkins_et_al.)/03:_Mineral_Properties/3.03:_Crystal_Shape
  58. https://www2.tulane.edu/~sanelson/eens211/twinning.htm
  59. https://www.gia.edu/hpht-and-cvd-diamond-growth-processes
  60. https://dash.harvard.edu/bitstreams/7312037c-a16a-6bd4-e053-0100007fdf3b/download
  61. https://newsreleases.sandia.gov/melting_diamonds/
  62. https://www.gia.edu/doc/WN04-v2.pdf
  63. https://www.gia.edu/doc/gg-gem-news-international.pdf
  64. https://commonminerals.esci.umn.edu/minerals-f/fluorite
  65. https://gotbooks.miracosta.edu/earth_science/chapter2.html
  66. https://minds.wisconsin.edu/bitstream/handle/1793/48105/PyriteShapes.pdf?sequence=1&isAllowed=y
  67. https://naturalhistory.si.edu/explore/collections/geogallery/10026573
  68. https://luminexspecimen.com/beginners-guide-to-gemstone-specimens/
  69. https://www.gemsociety.org/article/gems-and-minerals-facet-rough-or-samples/
Add your contribution
Related Hubs
User Avatar
No comments yet.