OpenFacet provides public, unauthenticated access to structured price data for natural, GIA-certified round diamonds with 3EX grading (cut, polish, symmetry) and non-fluorescent.

The API supports valuation, algorithmic pricing, and liquidity modeling by exposing core components of OpenFacet’s transparent pricing methodology. All responses are JSON-formatted and timestamped in UTC. Endpoints are served from: https://openfacet.net/api/.

GET /api/index.json – Composite Index & Basket

Returns the current Diamond Composite Index (DCX) and a representative basket of actively traded specifications.

Example: /api/index.json

Sample Response

{
  "dcx": 3568.6,
  "specs": [
    {
      "carat": 0.5,
      "clarity": "SI1",
      "color": "H",
      "cut": "Excellent",
      "log": 7.428,
      "per_carat": 1682.38,
      "price": 841.19,
      "weight": 0.22
    },
    ...
  ],
  "trend": 0.13,
  "ts": "2025-05-19T13:26:49Z"
}

Fields

• dcx: Composite per-carat price in USD.

• specs[]: Sample stones with:

  • price: Total price in USD
  • per_carat: USD per carat
  • log: $\log(\text{price})$ for interpolation
  • weight: Basket contribution

• trend: 24h change in dcx, in percent (e.g. 0.13 = +0.13%)

• ts: Timestamp in ISO 8601 format

GET /api/matrix.json – Price Matrices

Returns per-carat log price matrices across clarity and color, grouped by fixed carat bands.

Example: /api/matrix.json

Key Fields

• l: Map of carat band → flat array of $\log(\text{per-carat price})$ values. Each array is of length rows × cols, where:
  • rows = number of color grades (r)
  • cols = number of clarity grades (c)
• c: Clarity grade list (columns)
• r: Color grade list (rows)
• s: Shape [rows, cols] = [len(r), len(c)]

Price Calculation

To compute per-carat price:

$$ \text{price} = \exp(\log_\text{price}) $$

To interpolate $\log(\text{per-carat price})$ for non-discrete carat weights:

$$ \log_i = (1 - \lambda) \cdot \log(p_1) + \lambda \cdot \log(p_2) $$

Where:

• $p_1, p_2$ are per-carat prices at carat bands $c_1, c_2$
• $\lambda = \frac{c - c_1}{c_2 - c_1}$, with $c$ the target carat

After interpolation, apply Math.exp(log_i) to obtain the interpolated per-carat price.

GET /api/depth.json – Market Depth

Reports inventory depth across dimensions of carat, color, and clarity. Useful for liquidity-aware models or filtering.

Example: /api/depth.json

Structure

• clarity[carat][clarity]: Listings count per clarity grade at given carat
• color[carat][color]: Listings count per color grade at given carat
• colclar[color][clarity]: Total listings for each color × clarity pair
• ts: Snapshot timestamp

Example

"1.0": {
  "VS2": 1232
}

There are 1232 listings for 1.0ct VS2 diamonds at the snapshot time.

Data Freshness

Snapshots are updated periodically, typically once per 24h. Check the ts field in each response to ensure data recency.

For methodology details, see the About OpenFacet & DCX Methodology page.