Recycled Waterjet Red Garnet Sand

Material categories:

Mineral / Mineral based

Soil / Soil based (organic/mineral)

Identification number:


Sample produced by:


Sample date:

28 Sep 2023 (Received)

Sample condition:


Process-driven material

Within the Faculty of Architecture at the University of Hong Kong, students and faculty have several machining and fabrication technologies to work with to create prototypes, built interventions and models. One of these machining options is the waterjet cutter. Using jets of water it can cut material based off of a file specifying a form or pattern. Mixed in with the jet of water is an abrasive medium, typically this material is sand. In this case it is fine garnet sand. Garnet is a semi precious stone that is used due to its hardness and cutting ability. It is mined throughout the world, as well red garnet sand occurs naturally in river deposits within Australia.

This material is only used once and accumulates at the bottom of the waterjet machine, over time this must be cleaned out and the sand disposed of. Mixed in with the sand is a fine layer of silt, typically this is composed of fine particulate matter of the material that was cut, i.e. metal shavings, microplastics etc. Due to this small contamination the garnet sand is typically not reused within waterjet applications.

This material is an example of a byproduct that is produced within the architectural process. Practicing the ethos of material reuse within an institution where these ideas and concepts are taught is an example of the University of Hong Kong as a microcosm of Hong Kong as a whole.

Depth of sample extraction:

On/Above Ground

Slope at extraction point:

< 35°

Land Use:

Residential/ commercial/ government/ institutional/ community lot

Natural or imported material:



10R 4/4

Soil Structure

Organic Matter: 0.0 %

Coarse: 0.0 %

Sand: 83.0 %

Silt: 17.0 %

Clay: 0.0 %