1. What Makes a Well-Cut Gemstone?

A well-cut gemstone combines attractive appearance, suitable proportions, accurate facet placement and a good surface finish. A gemstone can have beautiful natural colour but still look disappointing if its cut is poorly executed.

When evaluating a finished stone, examine it under consistent lighting and from several viewing angles. Look for balanced proportions, a pleasing outline, good light return and visible cutting defects.

Remember that different gemstone varieties have different optical properties. Some stones are transparent, while others are translucent or opaque. The correct evaluation depends on the material and the intended cut.

2. Inspect Symmetry and Facet Alignment

Symmetry describes how evenly the gemstone's shape and facets are arranged. On a faceted stone, compare the left and right sides, the outline, the crown, the pavilion and the meeting points between facets.

• Outline: Check whether the stone has the intended shape and looks balanced.
• Facet junctions: Examine where neighbouring facets meet. Uneven junctions may indicate cutting inaccuracies.
• Table: On cuts with a table facet, check whether it appears centred and appropriately aligned.
• Girdle: Look for unusually thin, thick or uneven areas that may affect durability or appearance.
• Meet points: Inspect whether the facet edges meet cleanly and consistently.

Use a loupe or microscope for close inspection. Small differences may be difficult to see with the unaided eye. Not every gemstone shape requires perfect geometric symmetry, but the finish should suit the intended design.

3. Examine Polish and Surface Finish

Polish affects how smoothly light interacts with the gemstone's surface. Scratches, pits, polishing lines and dull areas can reduce its visual appeal.

Rotate the stone under a bright light and inspect the surface from different directions. Use magnification to distinguish surface marks from internal inclusions.

• Look for fine scratches on polished facets.
• Check for dull or unevenly polished areas.
• Inspect the girdle and facet edges for chips.
• Check the culet or pavilion area where applicable.
• Avoid aggressive repolishing until you understand the material and the cause of the defect.

A clean-looking surface does not prove that a gemstone is natural, untreated or valuable. Polish is only one part of a complete evaluation.

4. Evaluate Colour, Transparency and Light Performance

Colour is an important consideration for many coloured gemstones. Examine the stone under neutral, consistent lighting whenever possible. Very warm or strongly coloured lights can change how the colour appears.

Assess these features separately:

• Hue: The basic colour you see, such as blue, green, yellow or red.
• Tone: How light or dark the colour appears.
• Saturation: The strength or intensity of the colour.
• Transparency: How readily light passes through the material.
• Brilliance: The bright return of light from a faceted stone.
• Windowing: An area where the background may be visible through the stone because light escapes rather than returning to the viewer.
• Extinction: Dark areas that remain visible in certain viewing positions.

Turn the gemstone slowly and observe whether its appearance changes. Some changes are normal because of the stone's cut and optical properties. Judge its overall appearance rather than relying on a single viewing angle.

5. Measure Dimensions and Carat Weight

Record the finished gemstone's weight and dimensions. These measurements help with identification, inventory, comparison and future sales records.

• Use a suitable gemstone scale and check that it is level and properly zeroed.
• Record weight in carats (ct). One carat equals 0.2 grams.
• Measure length, width and depth in millimetres where appropriate.
• Record the gemstone shape and cut style.
• Keep the original rough weight separate from the finished weight.

Carat weight measures mass, not physical size or quality. Two gemstones with the same carat weight may have different dimensions because of their density, proportions and cut.

6. Understand What Influences Gemstone Value

Gemstone value depends on several factors, and no single measurement determines the price. Important considerations may include:

• Species and variety: Correct identification is essential before making meaningful comparisons.
• Colour: Colour quality and market preferences vary by gemstone type.
• Clarity: The visibility, location and type of inclusions can influence appearance and durability.
• Cut quality: Proportions, symmetry, polish and light performance affect desirability.
• Carat weight: Larger stones may command higher prices per carat in some markets, but this is not guaranteed.
• Treatments: Heating, filling, diffusion and other treatments can affect value and must be disclosed accurately.
• Origin: A reliably established geographic origin may influence market demand for certain gems, but origin should not be guessed from appearance alone.
• Documentation: A credible laboratory report may help support identification and treatment information.
• Market conditions: Demand, supply, buyer preferences and seller reputation affect actual selling prices.

Do not promise a specific value based only on a photograph, colour, weight or home test. For a commercial valuation, compare genuinely similar stones and seek qualified professional advice when needed.

7. Identification, Treatments and Responsible Disclosure

Visual inspection is useful, but it cannot reliably establish every gemstone's identity, natural or synthetic origin, treatment status or geographic origin.

Depending on the material, appropriate gemmological tests may include refractive index, specific gravity, magnification and spectroscopy. Each test has limitations, and some stones require advanced laboratory instruments.

For example, a refractive-index reading or specific-gravity measurement should be interpreted alongside other evidence. A single matching result is not proof of a gemstone's origin or natural status.

When selling or describing a gemstone, state what you know, explain any uncertainty and disclose treatments when known. Do not label a stone as natural, untreated or Sri Lankan-origin without adequate supporting evidence.

8. Final Inspection Checklist

Before you consider your cutting project complete, use this checklist:

• ☐ The outline and shape are appropriate for the design.
• ☐ Facets and junctions have been inspected under magnification.
• ☐ The surface has been checked for scratches, chips and polishing defects.
• ☐ Colour and light performance have been observed under consistent lighting.
• ☐ Weight and dimensions have been measured and recorded.
• ☐ The stone has been cleaned using a method suitable for its material and treatments.
• ☐ Identification and treatment claims are supported by suitable evidence.
• ☐ The gemstone has been stored safely to reduce the risk of scratches or damage.

9. Practical Exercise for Beginners

Choose one finished gemstone and complete an inspection record. Use a loupe, suitable lighting, a gemstone scale and measuring equipment if available.

1. Record the stone's reference number, shape and weight.
2. Measure its dimensions and note the measurement method.
3. Describe its colour and transparency without guessing its identity.
4. Inspect the facets and surface for visible defects.
5. Write down any tests performed and their results.
6. List the questions that would require additional testing or professional assessment.

The aim is to build careful observation and reliable record-keeping skills. Do not damage a gemstone to test its hardness, and do not use potentially damaging chemicals or heat.

10. Review the Complete SunMoonBay Course

Congratulations on reaching the final lesson. Revisit earlier lessons whenever you need to review equipment, cutting plans, faceting or polishing techniques.

Frequently Asked Questions

Does a heavier gemstone always have a higher value?

No. Value also depends on identity, colour, clarity, cut, treatments, documentation and market demand.

Can I identify a natural gemstone using a loupe alone?

A loupe can reveal useful features, but it cannot reliably establish every stone's identity, natural or synthetic status, treatment or geographic origin.

Why does my gemstone look dark from some angles?

Cut proportions, facet orientation, lighting and the stone's optical properties can create dark areas. Inspect it under different lighting and viewing positions.

Should I repolish every scratched gemstone?

No. First determine the material, the location and depth of the defect, and whether repolishing is appropriate. Unnecessary work can reduce the stone's weight or cause damage.

Does this inspection replace a gem laboratory report?

No. This lesson provides beginner inspection guidance. A qualified gemmological laboratory may be needed for dependable identification, treatment analysis or origin assessment.

SunMoonBay | Gemstone Education and Gem-Cutting Resources

You've Completed All 7 Steps!

Thank you for learning with SunMoonBay. Revisit the course whenever you need to review the fundamentals of gem cutting.

Congratulations! You Completed All 7 Steps

Thank you for learning with SunMoonBay. You can revisit the course introduction and review the lessons whenever you need.