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GIA GG practice questions

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Question 1Diamond Essentials and Diamond Grading

In the GIA clarity grading system, which clarity grade is assigned to a diamond in which inclusions are very difficult to see under 10x magnification and are only visible with effort?

  1. VS1
  2. VVS1 Correct answer.
  3. I1
  4. SI1

Explanation

The VVS category covers diamonds whose inclusions are very difficult for a skilled grader to detect at 10x. VVS1 is distinguished from VVS2 by how difficult the inclusion is to find, with VVS1 being at the top of that range.

Question 2Diamond Essentials and Diamond Grading

A polished diamond weighs 0.99 ct. According to GIA weight terminology, how is this stone described?

  1. A light carat
  2. A ninety-niner Correct answer.
  3. A half-carat
  4. A carat-and-a-half

Explanation

Trade shorthand calls stones just under a full carat 'ninety-niners' because cutters often leave them below the mark to avoid the higher price bracket. The term reflects the pricing jump that occurs at the one-carat threshold.

Question 3Diamond Essentials and Diamond Grading

Which diamond property is defined as the resistance of a polished surface to scratching?

  1. Cleavage
  2. Hardness Correct answer.
  3. Stability
  4. Toughness

Explanation

Hardness measures resistance to scratching on a surface, and diamond is the hardest mineral at 10 on the Mohs scale. Toughness, by contrast, describes resistance to breaking or chipping from a single impact.

Question 4Diamond Essentials and Diamond Grading

Which of the following is a common diamond inclusion consisting of a small crystal of a different mineral enclosed within the host diamond?

  1. Twinning line
  2. Graining
  3. Crystal Correct answer.
  4. Bearded girdle

Explanation

A crystal inclusion is a mineral grain trapped inside the diamond as it formed, and it is one of the most frequently observed clarity characteristics. Peridot and garnet are typical examples of such included crystals.

Question 5Diamond Essentials and Diamond Grading

In GIA color grading of a loose diamond, what is the standard reference environment for comparing the stone's color?

  1. Ultraviolet light in a darkened room
  2. A jeweler's display case under halogen lamps
  3. A controlled viewing environment with a colorless master set Correct answer.
  4. Direct sunlight against a white card

Explanation

Color is graded by comparing the stone to a set of master stones of known color in a controlled, neutral viewing environment. Daylight-equivalent lighting and a white background help reveal the true body color without tinting it.

Question 6Diamond Essentials and Diamond Grading

Which term describes the pattern of light and dark areas seen through the crown of a polished diamond when it is viewed face-up?

  1. Brilliance
  2. Scintillation Correct answer.
  3. Fire
  4. Dispersion

Explanation

Scintillation refers to the sparkle produced by flashes of light and the pattern of contrasting light and dark areas as the stone or observer moves. It is distinct from brilliance, which is the overall return of white light.

Question 7Diamond Essentials and Diamond Grading

A diamond has noticeable inclusions that are easy to see at 10x magnification and are also visible to the unaided eye. Which clarity grade best fits this description?

  1. SI2
  2. VS2
  3. I3
  4. I1 Correct answer.

Explanation

The Included category begins at I1, where inclusions are obvious at 10x and affect the stone's face-up appearance. I1 stones commonly show inclusions visible without magnification, unlike the SI range.

Question 8Diamond Essentials and Diamond Grading

Which diamond crystal form, an octahedron, is most commonly encountered in gem-quality rough?

  1. Two interpenetrating cubes
  2. A hexagonal prism with flat terminations
  3. Two pyramids joined base to base Correct answer.
  4. A dodecahedron with triangular faces

Explanation

The octahedron consists of two four-sided pyramids joined at a shared square base and is the classic habit of gem diamond. Its shape reflects the octahedral cleavage directions that cutters must plan around.

Question 9Diamond Essentials and Diamond Grading

A cutter is planning a stone from rough and wants the table oriented to minimize the risk of cleavage. Which statement about diamond cleavage is correct?

  1. Diamond has no cleavage and only fractures
  2. Diamond cleaves in six directions parallel to the dodecahedron
  3. Diamond has one cleavage direction parallel to the cube face
  4. Diamond has four cleavage directions parallel to the octahedral faces Correct answer.

Explanation

Diamond has four directions of perfect cleavage parallel to the faces of the octahedron. Impact along those planes can split the stone, so cutters orient the table and facets to avoid placing stress along them.

Question 10Diamond Essentials and Diamond Grading

A grader examines a diamond and sees a series of fine, parallel lines on a polished facet that do not penetrate the stone. What are these most likely to be?

  1. Twinning wisps
  2. Internal graining
  3. Indented naturals
  4. Polish lines Correct answer.

Explanation

Polish lines are fine, shallow striations left on a facet by the polishing process, and they remain on the surface. They differ from internal features because they do not extend into the stone.

Question 11Diamond Essentials and Diamond Grading

In GIA fluorescence terminology, what does the term 'strong' describe?

  1. The amount of fire seen face-up in daylight
  2. The number of internal graining lines present
  3. The degree of transparency of the stone
  4. The intensity of the visible fluorescence reaction under ultraviolet light Correct answer.

Explanation

Fluorescence is graded by the intensity of the reaction when the diamond is exposed to long-wave ultraviolet light. Terms range from none through faint, medium, strong, and very strong.

Question 12Diamond Essentials and Diamond Grading

A round brilliant is described as having a 'fish-eye' effect. What does this most likely indicate?

  1. The pavilion is too deep and the stone appears dark in the center
  2. The girdle is too thin and chipping has occurred
  3. The culet is polished to a point and reflects light back as a bright spot
  4. The table is too large or the crown angle too shallow, creating a reflection of the girdle Correct answer.

Explanation

A fish-eye appears when a shallow crown or oversized table allows the viewer to see the girdle reflected across the table. It reduces the stone's brightness and is considered an undesirable cut effect.

Question 13Diamond Essentials and Diamond Grading

Which proportion is defined as the angle between the girdle plane and the bezel facets on the crown?

  1. Pavilion angle
  2. Table percentage
  3. Star length
  4. Crown angle Correct answer.

Explanation

The crown angle is measured between the plane of the girdle and the slope of the crown's bezel facets. It strongly influences brightness and fire and is a key proportion in cut grading.

Question 14Diamond Essentials and Diamond Grading

A diamond is described as having a 'cloud' as its only clarity characteristic. How would a grader most likely characterize it?

  1. A surface-reaching fracture at the girdle
  2. A growth line running across the table
  3. A single large crystal inclusion near the pavilion
  4. A cluster of pinpoint inclusions that may reduce transparency if dense Correct answer.

Explanation

A cloud is a grouping of tiny pinpoint inclusions that scatter light and can create a hazy appearance when dense. Isolated clouds are common and often minor, but dense clouds can affect clarity grade and transparency.

Question 15Diamond Essentials and Diamond Grading

Which GIA color grade falls in the 'near-colorless' range?

  1. D
  2. K
  3. G Correct answer.
  4. M

Explanation

The near-colorless range covers G, H, I, and J. Grades D through F are colorless, while K through M fall in the faintly colored range.

Question 16Diamond Essentials and Diamond Grading

A diamond shows a distinct colored flash of blue when examined under a long-wave ultraviolet lamp. Which statement about this observation is most accurate?

  1. It indicates the diamond has an internal fracture
  2. It is a fluorescence reaction that can be noted on a grading report Correct answer.
  3. It confirms the stone is synthetic
  4. It proves the diamond has been treated

Explanation

Blue fluorescence under long-wave UV is a common natural reaction and is recorded as a graded characteristic on reports. Its presence does not by itself indicate synthesis or treatment.

Question 17Diamond Essentials and Diamond Grading

Why do cutters sometimes polish a tiny facet at the culet of a round brilliant?

  1. To reduce the amount of fluorescence
  2. To increase the stone's carat weight
  3. To prevent a sharp point from chipping Correct answer.
  4. To improve the stone's color grade

Explanation

A small polished culet facet replaces a fragile sharp point at the bottom of the pavilion, reducing the risk of chipping. An oversized culet, however, can be visible through the table and is undesirable.

Question 18Diamond Essentials and Diamond Grading

In clarity grading, which term describes a small, surface-reaching opening that runs into the stone at a shallow angle?

  1. Knot
  2. Chip
  3. Needle
  4. Feather Correct answer.

Explanation

A feather is a fracture that may reach the surface, and it appears as a thin, whitish, angled line. Shallow-angle feathers can reflect light and may raise durability concerns if they reach the girdle.

Question 19Diamond Essentials and Diamond Grading

A jeweler examines two diamonds of equal cut quality and equal color, one with SI1 clarity and one with VS2 clarity. What is the most likely relationship between their values?

  1. The SI1 stone is worth more only if it fluoresces
  2. The two stones should be worth the same because clarity does not affect value
  3. The SI1 stone is generally worth more because inclusions add character
  4. The VS2 stone is generally worth more because its inclusions are less noticeable Correct answer.

Explanation

All else being equal, higher clarity commands a higher price because inclusions are less visible. VS2 sits above SI1 in the clarity scale, so the VS2 stone typically carries a premium.

Question 20Diamond Essentials and Diamond Grading

Which statement best describes how a diamond's cut grade differs from its clarity grade?

  1. Cut grade evaluates color, while clarity grade evaluates weight
  2. Cut grade evaluates fluorescence, while clarity grade evaluates polish
  3. Cut grade evaluates the rough crystal shape, while clarity grade evaluates the finished stone
  4. Cut grade evaluates proportions and light performance, while clarity grade evaluates internal and surface characteristics Correct answer.

Explanation

Cut grade assesses how well the finished stone's proportions and facet arrangement return light, whereas clarity grade documents internal inclusions and surface blemishes. The two are independent factors in the overall assessment.

Question 21Diamond Essentials and Diamond Grading

A cutter is orienting a rough octahedron to maximize weight while managing cleavage risk. Which approach best reflects standard practice?

  1. Place all inclusions at the girdle to hide them
  2. Orient the table perpendicular to the cleavage planes to avoid impact stress Correct answer.
  3. Ignore cleavage and cut for maximum yield
  4. Saw parallel to an octahedral cleavage plane to minimize risk

Explanation

Cleavage planes run parallel to the octahedral faces, so orienting the table roughly perpendicular to them reduces the chance that impact will split the stone. Cutters balance this against yield and inclusion placement.

Question 22Diamond Essentials and Diamond Grading

A round brilliant has a pavilion angle that is too steep relative to its crown angle. Which light-performance outcome is most likely?

  1. A stronger blue fluorescence reaction
  2. Light leaking through the pavilion and a darker center Correct answer.
  3. A larger table reflection of the girdle
  4. Increased brightness across the whole stone

Explanation

When the pavilion is too steep, light entering the crown can be directed toward the pavilion facets at angles beyond total internal reflection. That light leaks out, producing dark areas and reduced brightness.

Question 23Diamond Essentials and Diamond Grading

A grading report notes an 'internal graining' that is faint and does not affect transparency. How should this be interpreted?

  1. It is a growth-related internal feature that is minor in this case Correct answer.
  2. It is a treatment that must be disclosed
  3. It is a surface polish defect that can be removed by repolishing
  4. It is a fracture that threatens durability

Explanation

Internal graining reflects irregularities in crystal growth and can appear as faint lines or a slight haze. When faint and non-affecting, it is a minor clarity characteristic rather than a durability or disclosure issue.

Question 24Diamond Essentials and Diamond Grading

Two stones have identical color, clarity, and carat weight, but one has excellent cut grade and the other has good cut grade. Which conclusion is most defensible?

  1. The good-cut stone will generally show better brightness because it retains more weight
  2. The excellent-cut stone will generally show better light performance and command a higher price Correct answer.
  3. The excellent-cut stone must have a lower clarity grade
  4. Cut grade has no effect on value when the other factors match

Explanation

Cut grade reflects how well proportions and facets return light, so an excellent cut generally produces better brightness, fire, and scintillation. Buyers pay a premium for superior light performance when the other factors are equal.

Question 25Diamond Essentials and Diamond Grading

A diamond is graded as having a 'medium' fluorescence with a yellow reaction. What is the most accurate interpretation for a buyer?

  1. The stone is definitely treated and should be rejected
  2. The yellow reaction proves the diamond is not natural
  3. The reaction guarantees the stone will look cloudy face-up
  4. The reaction is a graded characteristic that may or may not affect appearance, depending on the stone Correct answer.

Explanation

Fluorescence is graded by intensity and color of the reaction under UV, and its effect on appearance varies from stone to stone. Medium fluorescence with a yellow reaction is recorded as a characteristic, not as proof of treatment or a guarantee of cloudiness.

Question 26Diamond Essentials and Diamond Grading

Which of the four Cs refers to the relative proportions, symmetry, and polish of a polished diamond?

  1. Clarity
  2. Cut Correct answer.
  3. Color
  4. Carat weight

Explanation

Cut is the grade that assesses how well a diamond's proportions, symmetry, and polish interact to return light to the viewer. Carat weight measures mass, while clarity and color describe internal purity and body tint respectively. Cut is the only one of the four Cs that is largely determined by human craftsmanship.

Question 27Diamond Essentials and Diamond Grading

On the GIA clarity scale, which grade is the highest, reserved for stones with no inclusions or blemishes visible at 10x magnification?

  1. Loupe Clean
  2. Flawless Correct answer.
  3. Internally Flawless
  4. Very Very Slightly Included

Explanation

Flawless is the top clarity grade and requires that a grader see no internal or external characteristics at 10x magnification. Internally Flawless sits just below it because surface blemishes are permitted. Loupe Clean is a trade term, not part of the GIA clarity scale.

Question 28Diamond Essentials and Diamond Grading

A polished diamond is described as having a 'needle' as its only clarity characteristic. What does this term describe?

  1. A small feather that reaches the girdle surface
  2. A thin, elongated crystal or inclusion that appears as a line Correct answer.
  3. A cluster of tiny pinpoints spread over a wide area
  4. A twinning plane that reflects light as a colored flash

Explanation

A needle is a thin, elongated solid inclusion or crystal that appears as a line within the stone. It is distinct from a feather, which is a fracture, and from a cloud, which is a hazy cluster of pinpoints. Twinning planes produce twinning wisps rather than a needle.

Question 29Diamond Essentials and Diamond Grading

Which unit of weight is used for diamonds, and how many milligrams does one unit equal?

  1. Metric carat, equal to 100 milligrams
  2. Point, equal to 200 milligrams
  3. Metric carat, equal to 200 milligrams Correct answer.
  4. Grain, equal to 50 milligrams

Explanation

The metric carat is the standard unit for diamond weight and equals 200 milligrams, or one fifth of a gram. A point is one hundredth of a carat and is used for describing small fractions. Grain is a historical unit no longer used in modern diamond grading.

Question 30Diamond Essentials and Diamond Grading

A grader is assessing a diamond's color and places it face down in the grading tray next to masterstones. Why is the pavilion viewed through the girdle in this position?

  1. It allows the grader to measure the crown angle more accurately
  2. It reveals surface blemishes that face-up viewing would hide
  3. It prevents fluorescence from affecting the color comparison
  4. It removes the influence of body color seen through the crown and isolates the tint in the pavilion Correct answer.

Explanation

Viewing the pavilion through the girdle minimizes the effect of face-up color and lets the grader compare the tint concentrated in the pavilion against the masterstones. This orientation improves consistency in color grading. Crown angle measurement and blemish detection are unrelated to this procedure, and fluorescence is assessed separately under UV light.

Question 31Diamond Essentials and Diamond Grading

A diamond's girdle is described as extremely thin. What risk does this present to the finished stone?

  1. A higher likelihood that the stone will show a strong blue fluorescence
  2. A tendency for the culet to appear as a reflected dot
  3. An increased chance of chipping or abrasion along the girdle edge Correct answer.
  4. A noticeable reduction in the stone's fire and dispersion

Explanation

An extremely thin girdle leaves a fragile edge that is easily chipped or abraded during setting and wear. Girdle thickness does not control dispersion, fluorescence, or culet reflection. Those effects depend on other factors such as proportions and the stone's atomic structure.

Question 32Diamond Essentials and Diamond Grading

A grader observes that a diamond's pavilion main facets are slightly misaligned where they meet the girdle. Which symmetry feature does this describe?

  1. Star facet length
  2. Table facet off-center
  3. Pavilion facet alignment Correct answer.
  4. Girdle wave

Explanation

Misalignment of pavilion mains at the girdle is a symmetry defect in pavilion facet alignment. Girdle wave concerns the girdle's outline thickness variation, and table off-center concerns the table's position relative to the girdle. Star facet length is a proportion feature, not a description of facet misalignment at the girdle.

Question 33Diamond Essentials and Diamond Grading

A diamond is described as having a 'waxy' luster. Which statement best explains this observation?

  1. The stone is likely a simulant or has a surface condition rather than being a polished diamond Correct answer.
  2. The stone contains a large crystal inclusion at its center
  3. The stone has been cut with an extremely thin girdle
  4. The stone is a diamond with exceptionally high dispersion

Explanation

A well-polished diamond typically shows adamantine luster. A waxy or greasy appearance suggests a different material, such as a simulant, or a surface condition like an oily film. Dispersion, girdle thickness, and internal inclusions do not produce waxy luster.

Question 34Diamond Essentials and Diamond Grading

A cutter is examining a rough diamond and notes that it has a cleavage direction parallel to an octahedral face. What practical implication does this have for the cutter?

  1. The stone cannot be cut into a round brilliant without first removing the cleavage plane
  2. The stone can be split cleanly along that plane, but it is also vulnerable to accidental breakage there Correct answer.
  3. The stone will polish more easily in every direction because cleavage relieves internal strain
  4. The stone will show stronger fluorescence because of the cleavage structure

Explanation

Diamond has four cleavage directions parallel to octahedral faces, so a stone can be split along these planes, but the same planes are weak points where accidental damage may occur. Cleavage does not make polishing easier in all directions, does not forbid a round brilliant, and has no direct relationship to fluorescence.

Question 35Diamond Essentials and Diamond Grading

A grader notes that a diamond's fluorescence is described as 'faint' in GIA terminology. What does this indicate about the stone's reaction under ultraviolet light?

  1. No reaction at all under any ultraviolet wavelength
  2. A reaction visible only under short-wave ultraviolet light
  3. A reaction equal in strength to the 'strong' category
  4. A weak but discernible reaction compared with stronger categories Correct answer.

Explanation

Faint fluorescence indicates a weak but perceptible reaction under ultraviolet light, ranking below medium, strong, and very strong. It does not mean the absence of fluorescence, and it is not equivalent to the strong category. GIA reports describe the reaction observed under long-wave ultraviolet light.

Question 36Diamond Essentials and Diamond Grading

A round brilliant is cut with an excessively large table relative to its crown angle. Which face-up appearance is most likely?

  1. The stone will display a distinct fish-eye reflection around the girdle
  2. The stone will show unusually strong fire from the large table
  3. The stone may appear glassy and less brilliant because light leaks through the shallow crown Correct answer.
  4. The stone will show an exaggerated dark center under the table

Explanation

A very large table paired with a shallow crown tends to produce a glassy, less brilliant face-up appearance because light is not efficiently gathered and returned. Excessive fire and a fish-eye effect are associated with other proportion combinations, and a dark center typically relates to steep pavilion angles.

Question 37Diamond Essentials and Diamond Grading

A grading report lists 'extra facets' on the pavilion. How should this be interpreted in the context of cut grading?

  1. As a sign that the stone was cut from a twinned crystal
  2. As evidence that the stone has been fracture filled
  3. As an internal clarity characteristic that must be plotted on the diagram
  4. As a symmetry or finish detail that may lower the cut grade without affecting clarity Correct answer.

Explanation

Extra facets are finish details evaluated under cut grading; they are not internal clarity characteristics. They do not indicate twinning or treatment. They may reduce the cut grade if they are prominent, but they are not plotted as inclusions.

Question 38Diamond Essentials and Diamond Grading

A diamond is graded F color on the GIA scale. Which statement accurately describes this grade?

  1. Colorless, with no discernible tint even to a trained grader comparing against masterstones Correct answer.
  2. Near-colorless, with a slight tint detectable only by a trained grader
  3. Faintly tinted, with color noticeable face up to an untrained observer
  4. Lightly tinted, with an obvious yellow hue in the body of the stone

Explanation

F is the second-highest color grade and falls in the colorless range, meaning no tint is discernible when compared with masterstones under controlled conditions. Near-colorless begins at G, and faint or light tint descriptions apply to lower grades. The distinction between F and the near-colorless range is a common grading boundary.

Question 39Diamond Essentials and Diamond Grading

A cutter has a rough diamond with a large inclusion near the surface and must decide how to orient it. Which approach best reflects standard practice for maximizing value?

  1. Always orient the inclusion toward the pavilion so it cannot be seen face up
  2. Position the inclusion where it can be removed or hidden under a facet while preserving as much weight as practical Correct answer.
  3. Cut the stone to the smallest possible size to eliminate all inclusions
  4. Orient the inclusion directly under the table to keep the crown clean

Explanation

Cutters balance weight retention against clarity by placing inclusions where they can be removed or concealed under facets, often near the girdle or under the crown. Simply orienting an inclusion toward the pavilion or under the table can make it more visible face up. Reducing size drastically sacrifices value unnecessarily.

Question 40Diamond Essentials and Diamond Grading

A grader compares two stones: one shows a sharp, well-defined pattern of light and dark areas, and the other shows a diffuse, washed-out pattern. Which conclusion is best supported?

  1. Both stones have identical cut grades because pattern is not graded
  2. The first stone has a higher clarity grade than the second
  3. The second stone has better contrast and likely a higher cut grade than the first
  4. The first stone has better contrast and likely a higher cut grade than the second Correct answer.

Explanation

A sharp, well-defined light-and-dark pattern indicates good contrast, which is a component of cut grading. A diffuse, washed-out pattern suggests poorer contrast and typically a lower cut grade. Pattern contrast does not determine clarity grade, and it is a graded aspect of cut.

Question 41Colored Stone Essentials and Colored Stone Grading

In GIA colored stone terminology, which term describes the purity and intensity of a hue as affected by brown or gray components?

  1. Dispersion
  2. Hue
  3. Tone
  4. Saturation Correct answer.

Explanation

Saturation refers to the strength or purity of a color, describing how free it is from brown or gray modifiers. Hue is the basic color family, and tone is the lightness or darkness of that color. Together these three dimensions make up the GIA color description system for colored stones.

Question 42Colored Stone Essentials and Colored Stone Grading

A ruby is described as strongly purplish red with medium dark tone and vivid saturation. Which of these dimensions is the hue?

  1. Vivid
  2. Medium dark
  3. Strongly
  4. Purplish red Correct answer.

Explanation

Hue is the color family itself, so 'purplish red' names the hue with its modifier. 'Vivid' describes saturation, and 'medium dark' describes tone. 'Strongly' is a saturation modifier, not a hue.

Question 43Colored Stone Essentials and Colored Stone Grading

Which colored stone variety is defined by the presence of chromium as its coloring agent, producing red in corundum?

  1. Padparadscha sapphire
  2. Yellow sapphire
  3. Ruby Correct answer.
  4. Blue sapphire

Explanation

Ruby is red corundum colored by chromium, which is what separates ruby from all other corundum varieties. Blue sapphire is colored largely by iron and titanium, and yellow sapphire by iron. Padparadscha is a pinkish orange sapphire, not a chromium-red stone.

Question 44Colored Stone Essentials and Colored Stone Grading

In GIA colored stone clarity grading, which clarity type applies to transparent stones that show inclusions only under magnification?

  1. Type II
  2. Type I Correct answer.
  3. Type III
  4. Type IV

Explanation

Type I stones are those that are normally eye clean, so inclusions visible only under magnification still fit the top clarity grades. Type II stones typically contain some inclusions, and Type III stones are almost always included. There is no Type IV in the GIA colored stone clarity system.

Question 45Colored Stone Essentials and Colored Stone Grading

Which of these gemstones is classically described as having a single refractive index because it is amorphous?

  1. Opal Correct answer.
  2. Corundum
  3. Tourmaline
  4. Quartz

Explanation

Opal is amorphous, lacking crystal structure, so it is singly refractive and shows no birefringence. Quartz, corundum, and tourmaline are all crystalline and doubly refractive. This is why opal behaves differently from most faceted colored stones under the polariscope.

Question 46Colored Stone Essentials and Colored Stone Grading

Which treatment is commonly applied to emeralds to reduce the visibility of surface-reaching fractures?

  1. Irradiation
  2. Beryllium diffusion
  3. Heat treatment alone
  4. Fracture filling with oil or resin Correct answer.

Explanation

Emeralds are routinely filled with oil, resin, or similar substances to mask surface-reaching fractures and improve apparent clarity. Irradiation and beryllium diffusion are not standard emerald clarity treatments. Heat alone does not fill fractures in emerald.

Question 47Colored Stone Essentials and Colored Stone Grading

Which gemstone is the classic source of the phenomenon called asterism, seen as a six-rayed star?

  1. Ametrine
  2. Sunstone
  3. Moonstone
  4. Star sapphire Correct answer.

Explanation

Asterism in star sapphire is caused by needle-like rutile inclusions oriented in three directions, reflecting light into a six-rayed star. Ametrine and sunstone do not show asterism, and moonstone shows adularescence rather than a star.

Question 48Colored Stone Essentials and Colored Stone Grading

Which term describes a gemstone's resistance to scratching, as measured on a relative scale?

  1. Stability
  2. Cleavage
  3. Hardness Correct answer.
  4. Toughness

Explanation

Hardness measures resistance to scratching and is ranked on the Mohs relative scale. Toughness instead describes resistance to breaking or chipping from impact. Cleavage refers to breaking along structural planes, and stability relates to resistance to chemical or thermal change.

Question 49Colored Stone Essentials and Colored Stone Grading

A client asks why a blue sapphire's color looks uneven across a faceted stone. Which explanation best reflects how pleochroism affects appearance?

  1. The stone changes color permanently when heated
  2. The stone reflects light from its pavilion facets only
  3. The stone fluoresces differently under ultraviolet light
  4. The stone shows different colors when viewed from different crystallographic directions Correct answer.

Explanation

Pleochroism means a doubly refractive stone can show different colors or color intensities when viewed along different crystallographic directions. A cutter can orient the rough to place the best color through the table. Fluorescence and internal reflection are separate phenomena, and heat does not cause this directional color variation.

Question 50Colored Stone Essentials and Colored Stone Grading

A sapphire is graded as having strong saturation but very dark tone. How should a grader describe the likely overall appearance?

  1. Vivid and bright
  2. Pale and grayish
  3. Intense but dark Correct answer.
  4. Opaque and dull

Explanation

Tone and saturation are separate dimensions, so a stone can be strongly saturated yet very dark. In such a case the color is intense but lacks brightness because of the low tone. Pale or grayish descriptions would require low saturation, not strong saturation.