# What is a stone aggregate: definition, types and how it is made

Stone aggregate —sand and gravel— is 60–70% of concrete's volume (GCC, 2020). What it is, its types, and how a quarry produces it.

By the Grupo Server editorial team · [Editorial policy](https://gruposerver.com.mx/en/blog/editorial/)

Published September 2, 2026 · Updated September 9, 2026

A stone aggregate is the rock-based material —sand and gravel— combined with cement and water to produce concrete, or used loose in a project's bases and fills. Per GCC's technical data sheet from August 2020, stone aggregates make up 60 to 70% of the volume of hydraulic concrete, and in Mexico they must meet NMX-C-111-ONNCCE-2018, in force since November 2018.

**Key facts**

- Stone aggregates are 60–70% of concrete's volume, per GCC's technical data sheet (August 2020).
- They split into fine aggregate (sand) and coarse aggregate (gravel) under NMX-C-111-ONNCCE-2018.
- The SGM defines a quarry (banco de materiales) as an open-pit excavation for stone material (2023 Anuario, p. 502).
- Mexico's Mining Law (art. 5, sec. IV and V) exempts construction stone material from its concession regime.
- Triturados Gramol, part of Grupo Server, runs two aggregate plants: in Coahuila and San Luis Potosí.

## What is a stone aggregate?

A stone aggregate is any rock-based material — fragments of stone of different sizes — used as a construction component, either mixed with cement and water to make concrete, or used loose for bases, fills and paving. The name "stone" (pétreo) refers to its mineral origin, as opposed to materials like steel or wood.

Its role in concrete is not just filler: it provides most of the mix's volume and a large share of its mechanical strength. That is why its quality — grading, cleanliness and the strength of the source rock — is regulated under [NMX-C-111-ONNCCE-2018](https://dof.gob.mx/nota_detalle.php?codigo=5543504&fecha=12/11/2018) before it can go into structural concrete.

Outside of concrete, stone aggregate is also used without cement: as loose material for fills, for a pavement's layers — ballast, base and sub-base — or as the running surface on unpaved roads. Those uses call for different quality requirements than structural concrete, but the material is still stone aggregate in the technical sense of the term.

## What types of stone aggregate are there?

Stone aggregates are classified mainly by two criteria. The first is particle size: fine aggregate, sand, and coarse aggregate, gravel, as defined by standard NMX-C-111. The second is the material's source: river aggregate, with grains rounded by water wear, and crushed aggregate, produced by breaking rock at a quarry, with angular grains.

| Criterion | Type | Description |
| --- | --- | --- |
| Size | Fine aggregate (sand) | Small particles; mortar and the fine component of concrete |
| Size | Coarse aggregate (gravel) | Larger particles; coarse component of concrete and base courses |
| Source | River | Grains rounded by water |
| Source | Crushed | Angular grains, produced at a quarry |

Beyond these two basic aggregates come derived products with different degrees of processing, such as [the ballast, base and asphalt surface course](https://gruposerver.com.mx/en/blog/balastro-base-y-carpeta-que-son-y-para-que-sirven/) used in a pavement's structure — all of them also stone aggregates, with different grading and compaction.

Recognizing which category a given order falls into matters when comparing suppliers: a request for "aggregate" without specifying fine or coarse, river or crushed, or which pavement layer it is meant for, is not a complete specification, and it makes two suppliers' offerings hard to compare on equal terms.

## What is a quarry (banco de materiales)?

A banco de materiales — a quarry, in the sense used in Mexican mining statistics — is the physical source of stone aggregate. Per the glossary of the [Anuario Estadístico de la Minería Mexicana 2023](https://www.sgm.gob.mx/productos/pdf/Anuario_2023_Edicion_2024.pdf), published by Mexico's Geological Survey (SGM, 2024 edition, p. 502), a banco de materiales is an "open-pit excavation intended to extract stone material for the construction industry."

Even though extraction is done in the open air, Mexico's [Mining Law](https://www.diputados.gob.mx/LeyesBiblio/pdf/LMin.pdf), in article 5, sections IV and V, exempts from its concession regime rocks or their decomposition products that can only be used to manufacture construction materials, as well as rock decomposition products mined in the open air. That legal distinction is why a construction stone-aggregate company does not operate under a mining concession.

## How does rock become finished aggregate?

The general process has three stages. First, [extraction at the quarry, separating rock](https://gruposerver.com.mx/en/blog/que-es-un-banco-de-materiales-y-como-se-regula/) from its surroundings. Second, crushing, where mechanical equipment reduces the rock to smaller fragments. Third, screening, where the crushed material passes through mesh of different openings to sort it into commercial fractions — sand, 3/8", 3/4", 1", 1½" gravel, among others — that are then sold separately or combined depending on the use.

Each resulting fraction must meet the grading of its corresponding standard before leaving the plant, and each aggregate type's bulk density — loose or compacted — determines how much material a given load volume represents.

That process — extraction, crushing and screening — is what sets a stone-aggregate company apart from a plain, unprocessed quarry: the value added is turning irregularly sized rock into commercial fractions with controlled, consistent grading, ready to use on site without further processing.

Quality control usually runs alongside each stage rather than only at the end: the source rock is checked before crushing, the crushed output is checked as it is screened, and each finished fraction is checked again before it leaves the plant, so a grading failure is caught close to where it happened.

## How does Grupo Server help?

Triturados Gramol, a Grupo Server company founded in 2003, produces stone aggregates —gravel, sand, ballast, base and asphalt mix— with two operating plants, one in Coahuila and one in San Luis Potosí. It is the group's company dedicated entirely to this process, from quarry to finished product.

You can review [Triturados Gramol's profile](https://gruposerver.com.mx/en/empresas/triturados-gramol/), learn about the group's [industrial parks](https://gruposerver.com.mx/en/parques/), which also depend on infrastructure and materials, or write in through the [contact form](https://gruposerver.com.mx/en/contacto/) for a quote.

## Frequently asked questions

### What is a stone aggregate?

It is the rock-based material —sand and gravel— combined with cement and water to make concrete, or used loose in bases and fills. It makes up 60 to 70% of concrete's volume, per GCC (August 2020).

### What types of stone aggregate are there?

They split by size into fine aggregate (sand) and coarse aggregate (gravel), and by source into river material or material crushed at a quarry, under NMX-C-111-ONNCCE-2018.

### What is a quarry (banco de materiales)?

Per the glossary of the SGM's Anuario Estadístico de la Minería Mexicana 2023, a banco de materiales is an 'open-pit excavation intended to extract stone material for the construction industry.'

### Is stone aggregate extraction considered mining?

Mexico's Mining Law, article 5, sections IV and V, exempts from its concession regime rocks or their decomposition products that can only be used to manufacture construction materials.

### How does rock become finished aggregate?

The general process has three stages: extraction at the quarry, crushing the rock to the required sizes, and screening to sort each fraction by particle size.

## Topics

- Grupo Server
- Triturados Gramol
- Saltillo
- Coahuila
- San Luis Potosí
- NMX-C-111-ONNCCE-2018

## Sources

- [SGM, Anuario Estadístico de la Minería Mexicana 2023 (2024 ed.), glossary p. 502](https://www.sgm.gob.mx/productos/pdf/Anuario_2023_Edicion_2024.pdf)
- [Ley Minera, art. 5 sections IV and V (reform DOF 08-05-2023)](https://www.diputados.gob.mx/LeyesBiblio/pdf/LMin.pdf)
- [GCC, Aggregates technical data sheet (August 2020)](https://www.gcc.com/wp-content/uploads/2020/08/FT-0620-AGREGADOS-PÉTREOS.pdf)
- [NMX-C-111-ONNCCE-2018, Diario Oficial de la Federación, November 12, 2018](https://dof.gob.mx/nota_detalle.php?codigo=5543504&fecha=12/11/2018)
- Triturados Gramol company profile

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