Borax (also known as sodium borate decahydrate; sodium pyroborate; birax; sodium tetraborate decahydrate; sodium biborate) is a natural mineral compound (Na2B4O7 • 10H2O). It was discovered over 4000 years ago.
 
Borax is usually found deep within the ground, although it has been mined near the surface in Death Valley, California since the 1800s. Although it has numerous industrial uses, in the home borax is used as a natural laundry booster, multipurpose cleaner, fungicide, preservative, insecticide, herbicide, disinfectant, dessicant, and ingredient in making 'slime'.
 
Borax crystals are odorless, whitish (can have various color impurities), and alkaline. Borax is not flammable and is not reactive. It can be mixed with most other cleaning agents, including chlorine bleach.