The evidence does not specifically name quartz or establish the product’s pH and chemistry.
Why
Windex Original is identified as a hard-surface cleaner, and no quartz prohibition or hazardous classification is provided. Normal use on intact quartz is reasonably expected to be compatible, but the evidence is not quartz-specific.
What to do
Use only as directed on the label; test a small inconspicuous area first and avoid prolonged contact or allowing the product to dry.
pH
Not stated in the provided evidence.
Relevant chemistry
The provided evidence identifies it as a hard-surface cleaner but does not establish pH or specific chemistry classes.
Source: official product page ↗