1. Shard characteristics

Before talking about products, let's talk about the properties of ceramic shards. Ceramic shards are agglomerates of grains of different origins:

• residual crystals of quartz, potassium feldspars or soda-lime feldspars (plagioclase) and mica from the original rocks;

• new small crystals formed during firing: quartz, mullite, hematite, calco-aluminum silicates (e.g. pyroxene, gehlenite).

These crystals are bound together by the glassy matrix of the melting elements. The theoretical density of this material is around 2,600-2,750 kg/m ³ (the density of quartz is 2,650 kg/m ³ , but that of hematite is 5,250 kg/m ³ ).

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