Digital Gemology

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53 free lessons in six topics · 23 videos

Free lessons on diamonds and how they are cut and graded. Pick what you are curious about and start there. Every lesson stands on its own: a few minutes of reading, a free tool to try, and a quick quiz at the end.

Topics

Pick a topic you are curious about. Read one lesson or all of them, in any order.

Watch: one idea in 90 seconds

Six short animations with captions on screen. Each one opens its lesson.

Data

Digital Gemology Cut Performance Index: how every cut we sell scores on brilliance, fire, scintillation and more, in diamond, moissanite, cubic zirconia, ruby, sapphire, emerald and amethyst. Sortable tables, the method, and the data to download.

All lessons

The four Cs of diamonds

  1. The 4 Cs of diamonds explained: carat, color, clarity and cut
  2. Carat weight vs size: why a 2 ct diamond isn't twice as big
  3. The diamond color scale, D to Z: where you first see a tint
  4. Fancy color diamonds and fluorescence: beyond the Z grade
  5. The diamond clarity scale explained, from FL to I3
  6. Diamond cut grade: Excellent vs Poor, side by side
  7. How a diamond cut grade is set: proportions, polish and symmetry
  8. Putting the 4 Cs together: which C to spend on

Diamond anatomy and proportions

  1. The parts of a diamond: crown, girdle and pavilion
  2. Diamond measurements explained: diameter, depth and percentages
  3. Diamond table percentage: what table size does to the light
  4. Crown angle and crown height in a round diamond
  5. Pavilion angle and pavilion depth: how a diamond keeps the light in
  6. Star length and lower half length in a round brilliant
  7. Diamond girdle thickness: thin, medium, thick and what it costs you
  8. The diamond culet: none, pointed or large
  9. How to read diamond proportions: decode a stone from its numbers

How to read a diamond grading report

  1. What a diamond grading report is, and what it isn't
  2. The ID section of a diamond report: number, shape and measurements
  3. The grades on a diamond report: color, clarity and cut
  4. What "ideal cut" means on a diamond report
  5. Polish, symmetry and fluorescence on a diamond report
  6. The clarity plot: how to read the inclusion map on a report
  7. How to read the proportion diagram on a diamond report
  8. Comments, treatments and lab-grown origin on a diamond report
  9. How to read a diamond grading report, start to finish

Diamond vs moissanite

  1. Diamond vs moissanite: two look-alikes, two different materials
  2. Diamond vs moissanite properties: hardness, refractive index, dispersion, density
  3. Moissanite's refractive index, and why it needs its own cut
  4. Why moissanite shows more fire than diamond
  5. The loupe test: doubled facet edges in moissanite
  6. Moissanite vs diamond: same size, different carat weight
  7. Moissanite color and fluorescence compared with diamond
  8. Diamond testers and moissanite: what the instruments say
  9. Moissanite certificates vs diamond grading reports
  10. Moissanite vs diamond: wear, care and cleaning

Historic diamond cuts: the history of the brilliant

  1. The old single cut: eight facets and a lot of fire
  2. The Mazarin cut: the first brilliant
  3. The Peruzzi cut: today's crown arriving early
  4. Old mine cut diamonds: tidier, not brighter
  5. Old European cut diamonds: when the outline went round
  6. Tolkowsky's 1919 ideal cut: the brilliant that was calculated
  7. Hearts and arrows diamonds: precision you can see
  8. Past the 1919 ceiling: DG-Miliano and the modern brilliant

The bow-tie effect

  1. The bow-tie effect in diamonds: what it is
  2. Which diamond shapes get a bow-tie: oval, pear, marquise and more
  3. Bow-tie in the stone, sometimes on your finger: tilt and head shadow
  4. What causes a bow-tie? Four explanations, tested
  5. Is a bow-tie always there? How much is normal
  6. Bow-ties and grading reports: what the numbers can't tell you
  7. Why bow-ties are still cut: weight, outline and cost
  8. Fixing a bow-tie: the steep belly of DG-Bowtie
  9. How to check a stone for a bow-tie: a bench routine

Quick quizzes

Every lesson ends with a few questions, and five topics have a quiz of their own. No account, nothing saved: pick an answer and see at once if you got it, and why.

All the quizzes

The cuts behind the lessons

Every cut in these lessons is in our library, with 3D models and cutting files for sale.

Browse the cuts