Prepare for the AGS AJP core topics by practicing precise gemological language: distinguish carat from karat, shape from cut quality, natural from lab-grown from simulant, and observation from graded claims. Use the worked scenarios and self-check rubric below, then confirm administrative details such as eligibility and exam format directly with the American Gem Society at americangemsociety.org.
Carat vs. Karat: Two Units You Must Never Swap in a Sentence
Carat measures gem weight; karat measures the fineness of gold. Because both words appear on the same sales floor, the AJP core topics reward learners who can define each unit and convert between them without hesitation.
Start with the metric carat: one carat equals 0.2 grams, so a five-carat gem weighs one gram. In a worked example, a 2.00 ct diamond weighs 0.4 g. Prices do not scale linearly with weight; larger stones are rarer per carat, so two 1.00 ct stones together are typically worth less than one 2.00 ct stone of similar quality. That rarity step is a concept worth being able to explain, not just state.
Karat belongs to metal, not stones. Pure gold is 24 karat, and each karat is one twenty-fourth of the alloy: 18k gold is 18/24, or 75 percent gold, while 14k is roughly 58.3 percent. When a customer asks why a ring is stamped 750, you can connect the stamp to 18k fineness. Practicing both conversions together builds the habit of asking yourself, before you speak, whether the question concerns a stone or a setting.
- 1 ct = 0.2 g, so 5 ct = 1 g; check any conversion by multiplying carats by 0.2
- 18k = 75% gold, 14k = 58.3% gold, 24k = pure gold
- A stamp of 750 on jewelry corresponds to 18k fineness
The 4Cs: Separating Graded Attributes from Honest Observation
Color, clarity, cut, and carat weight are graded attributes assigned under standardized conditions. Core AJP preparation means knowing what each C measures and refusing to state a grade you cannot document.
Each C answers a different question. Carat weight is measured on a scale. Color describes how little or much body color a diamond shows, conventionally on letter scales running from colorless toward noticeable tint. Clarity describes the visibility, size, number, and position of internal characteristics and surface features. Cut evaluates how well a stone's proportions and finish return light. Study each C as a system with defined conditions, not as a loose adjective you can apply at will.
The practical discipline is separating two kinds of statement. A graded claim, such as a color letter or a clarity grade, requires a grading report or your own standardized assessment; it is a documented conclusion. An observation, such as 'this stone faces up white next to the others in the case' or 'I can see a small dark spot here,' requires no authority and is always safe to give. In conversation, lead with observations and attach grades only to documents you can point to.
Natural, Lab-Grown, and Simulant: A Three-Category Classification That Prevents Misdescription
These are three distinct categories: natural diamond, lab-grown diamond, and diamond simulant. Confusing them is a factual error with ethical consequences, so practice assigning every stone to exactly one category.
Scenario one: a customer picks up a moissanite ring and asks, 'Is this a real diamond?' A plausible mistake is answering 'yes, it's lab-created' or, at the other extreme, 'no, it's fake.' Both answers misclassify the stone. The better decision is to sort it into the correct category: moissanite is a diamond simulant, a different gem material that resembles diamond in appearance. A lab-grown diamond, by contrast, is diamond by composition; only its origin differs from a natural stone. 'Real' is the customer's word, and your job is to replace it with precise language.
Why it matters: misdescription is exactly the kind of consumer-protection failure the American Gem Society's mission of ethical conduct and consumer protection exists to prevent. A customer told a simulant is a lab-grown diamond will have paid a simulant price for a diamond expectation. A customer told a lab-grown diamond is 'fake' is misled in the opposite direction. Practice the three-way sorting until it is automatic, using the table below as a decision aid.
| Category | What it is | Example | Accurate one-line description |
|---|---|---|---|
| Natural diamond | Diamond formed in the earth | A natural round brilliant | 'This is a natural diamond; the report confirms its grades.' |
| Lab-grown diamond | Diamond grown in a laboratory; chemically diamond | A lab-grown oval | 'This is a lab-grown diamond, real diamond by composition, grown rather than mined.' |
| Diamond simulant | A different material that imitates diamond's look | Cubic zirconia or moissanite | 'This is not diamond; it is a simulant, a separate gem material.' |
Cut Grade vs. Shape vs. Cutting Style: Untangling Three Words Customers Treat as One
Shape is the outline, cutting style is the facet arrangement, and cut quality is an assessment of how well the stone was fashioned. The AJP core topics expect you to use the three terms distinctly.
In a worked example, 'a round brilliant' packs two answers into one phrase: round is the shape, brilliant is the cutting style. An emerald cut is a step-cut style in a rectangular outline. A princess cut is a square outline usually finished with a brilliant-style facet pattern. When you describe a stone, name the outline first, then the facet arrangement, and only then, if you have documentation or a standardized basis, comment on cut quality. Three terms, three different observations, three parts of the same sentence.
Cut quality is the term most easily overstated. Saying 'it's a well-cut stone' as a casual impression is different from citing a cut grade on a report. Study the vocabulary of light return, sparkle, and pattern as observable qualities: 'this stone returns a lot of light and shows strong sparkle in the case light.' Those are claims you can defend from direct viewing. Reserve graded cut language for documents, and you will never be caught promising a grade you cannot support.
Clarity Characteristics: Describing Inclusions Without Issuing a Grade
Inclusions are internal characteristics and blemishes are surface features; clarity grades are assigned under defined magnification conditions. Learn to describe a feature's position, size, and nature in observation-only language.
Scenario two: under the case lighting, you can see a small dark spot in a stone with your unaided eye, and the customer asks, 'What clarity grade is this?' The tempting mistake is to quote a clarity grade from memory of similar stones or to reassure the customer that it is 'eye-clean so it's basically VS.' The better decision is to describe what you actually observe: 'There's a small dark inclusion near the edge of the table; I can see it without magnification. The clarity grade itself is on the report, and I'll show you where it's plotted.' You have answered honestly and redirected to documentation.
The distinction matters because clarity grading happens under controlled conditions with trained eyes and defined conventions; a glimpse under store lighting is not that process. Two descriptions serve different purposes: 'I can see a dark spot here' is an observation the customer can verify by looking, while 'this is a VS stone' is a graded claim that belongs to the report. Practice both kinds of sentence for the same stone until switching between them feels natural.
Treatment Vocabulary: Framing What Is Known, Documented, and Undetermined
Core topics include treated gems: stones whose appearance has been deliberately improved. Preparation means knowing common treatment categories and disclosing status honestly, including when status is unknown or undocumented.
Study treatment as a set of named categories rather than a single idea. Colored stones, for example, are commonly subjected to processes that improve or change color, and clarity-related processes exist for some materials as well. For each category you study, be able to state what the treatment does, why it is done, and whether it is stable under normal wear. The learning goal is not a memorized list but a framework: any claim about a stone's appearance or durability may depend on whether it has been treated.
The disclosure habit has three parts: what you know from direct observation, what the accompanying documentation states, and what remains undetermined. A safe customer sentence has that same structure: 'The report describes this stone as heat treated; that's a standard, stable process for this material, and here is what the document says.' If you have no documentation, say so plainly rather than guessing. Practicing the three-part structure keeps you accurate on the material and prepares you for the professional communication the AJP title represents.
A Six-Week Study Sequence, a Store-Case Exercise, and Readiness Checks
Build the habit of precise language through a six-week sequence that pairs each topic with spoken practice, then verify readiness with a self-check rubric rather than hoping familiarity will carry you through.
A suggested sequence: weeks one and two cover units and the 4Cs, ending with the carat and karat conversions recited from memory; week three covers the natural, lab-grown, and simulant categories using the classification table; week four covers shape, cutting style, and cut-quality vocabulary; week five covers clarity description and treatment disclosure; week six is review and spoken rehearsal. In each week, spend at least one session saying descriptions out loud, because the exam-relevant skill is fluent, precise phrasing rather than silent recognition.
Practical exercise: visit any jewelry counter or use product photos, pick three stones, and for each one write a two-sentence description containing one observation and, if documentation is visible, one documented claim. Expected observations: you can state the category (natural, lab-grown, or simulant) only if it is labeled or documented; you can always state shape and cutting style from viewing; you can describe clarity features without quoting a grade. Score yourself against the rubric below and repeat until every line passes consistently.
- Rubric 1: State carat-to-gram and karat-to-percent conversions instantly and correctly
- Rubric 2: Assign three stones to the correct category (natural, lab-grown, simulant) with a justified one-line description
- Rubric 3: Separate shape, cutting style, and cut-quality claims in a single accurate sentence
- Rubric 4: Describe a visible clarity feature in observation-only language without quoting a grade
- Rubric 5: Frame a treatment disclosure in three parts: observed, documented, undetermined
- Self-check scores are learning milestones for your own review, not predictions of any exam result
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.