It's short for engineered quartz. Usually, when we say quartz, we mean engineered( synthetic) quartz.
If you mention natural quartz, it is Quartzite.
Artificial quartz stone, also known as reconstituted quartz, is the production of several raw materials organized by the manufacturer.
Raw materials: a variety of natural quartz sand, quartz powder, pigments, resin and other materials. By mixing, vacuuming, pressing, heating curing, polishing and other processes.
The advantages of engineered quartz: high hardness, no obvious colour difference, scratch resistance, non-absorption, stain resistance.
Disadvantages of engineered quartz:
Compared with natural stone, the engineered stone doesn’t have rich colours.
Granite refers to natural granite, is directly from the mining, after cutting, polishing.
The hardness of granite is greater than that of natural marble. The hardness of granites varies from place to place, as most Brazilian granites have a high hardness.
Advantages of natural granite: natural, durable.
Disadvantages of natural granite: Color variation, pinholes, more brittle.
Although the hardness of quartzite is very high. But crushed quartz grits, mixed with resin, the hardness of artificial quartz surfaces is lower than quartzite, also generally lower than granite hardness. But it's much more flexible than granite.