A purity figure on a data sheet looks like a promise. Sometimes it is one. More often it describes a sample that was tested, a range the material has historically fallen in, or a property of the mineral taken from reference data. All three are useful. None of them is the same thing as a guaranteed limit, and a buyer who treats them as interchangeable can end up specifying against a number nobody agreed to ship.
The fix is simple: read the status next to each figure before you read the figure.
Six statuses, six different commitments
These are the statuses AragoCor publishes its values under. Other suppliers use other labels, but the underlying distinctions are the ones worth asking about.
| Status | What it means | Does it bind a shipment? |
|---|---|---|
| Representative analysis | A measured laboratory result on a sample of the material. It describes what was tested. | No |
| Published range | A range published for the material. Neither a single measurement nor a contractual limit. | No |
| Published reference | A property of the mineral species from published reference data, not a test of the supplier’s material. | No |
| Product specification | A value the grade is supplied against, stated as a minimum or maximum. | Yes |
| Customer specification required | No published value; the figure is set by the buyer’s specification at order. | Yes, once agreed |
| Lot-specific COA | A value that exists only on the certificate of analysis (COA) for an individual dispatched lot. | That lot |
A worked example: AragoCor’s own sheet
Here is how the figures on the AragoCor master technical data sheet read once you apply those labels.
- 96.17% CaCO3 and 38.51% elemental calcium are representative analysis by ASTM C 25, Bowser-Morner report 124914A. The laboratory, method and report are named, which is what makes the figure checkable. It is not a guaranteed minimum.
- Surface area above 1.7 m2/g is representative analysis from Keck Lab.
- Grade sizing — AG-CAL 0.2–0.5 mm, GL-CAL below 0.1 mm and WT-CAL 1–3 mm — is a published range for each grade. PL-CAL has no published sizing: it is supplied to customer specification.
- Moisture as received, 5–10%, is a published range, and the words “as received” matter. A moisture figure means little until you know whether it describes material as shipped or after drying.
- Decomposition temperature of approximately 825 °C and CAS 1317-65-3 are published reference values: properties of the mineral, not results from a sample.
Reading the particle-size table
Sizing is where data sheets differ most. A mesh number names a sieve; the opening behind it is what matters, so state openings in millimetres or micrometres when you write a specification. Then check what the table reports: the share retained on each sieve, the cumulative share retained, or the cumulative share passing. Supplier sheets use all three, and the same numbers mean different things under each heading.
Powder reports often give D10, D50 and D90 instead: the sizes below which a stated share of the sample falls, by a stated method and on a stated basis. Laser diffraction and sieving do not give interchangeable results, and a median alone says nothing about the coarse tail. On AragoCor’s sheet, sizing is stated by grade and custom classification separately; choosing an aragonite grade explains the difference.
Where the guarantee actually lives
If none of those figures binds a shipment, what does? Two documents, and you should expect both from any supplier you qualify.
A guaranteed specification is agreed in writing per contract and confirmed per lot by certificate of analysis. The data sheet tells you what the material is; the contract and the lot certificate tell you what you will receive.
That is why a data sheet full of representative figures is not a weakness. It is an honest description of the material, and it gives you the starting point for the limits you then negotiate. A sheet that prints every value as a hard minimum, with no laboratory or method behind it, deserves more scrutiny, not less.
Checking a certificate of analysis
The certificate of analysis is the lot’s own record. Before accepting a delivery, confirm that the lot number on the certificate matches the shipment, that each result is on the basis your specification uses — CaCO3, elemental calcium or CaO; as received or dry — and that the method is the one agreed. A result reported below a detection limit is not the same as zero, and it only answers your question if that limit sits below your own.
Then compare each result with the agreed limit, not with the data sheet. A lot can sit away from the representative analysis and still meet the specification, or match the data sheet and still miss a limit that was never on it. File the certificate with the purchase order and the specification it was accepted against.
Five questions to ask any supplier
- What is the status of this figure? Measured, published range, reference, or specification.
- Which laboratory, method and report produced it? A figure with no source cannot be verified.
- On what basis? As received or dried, and for which grade or sizing.
- Which values appear on the lot certificate? Those are the ones you can hold a shipment to.
- Does the CAS number match the material you are buying? Natural aragonite is CAS 1317-65-3. A sheet citing a different identifier may be describing a different material.
The technical library carries the controlled sheet for every grade, and the contact form is the route to the safety data sheet and source documentation.
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