Tequila is made from blue agave, primarily in the area surrounding the city of Tequila. Tequila is a type of mezcal, not the other way around. The distinction is that tequila must use only blue agave plants rather than any type of agave.
The red volcanic soil in the region around the city of Tequila is particularly well suited to the growing of the blue agave, and more than 300 million of the plants are harvested there each year.
Blue agaves grown in the highlands are larger in size and sweeter in aroma and taste. Agaves harvested in the lowlands have a more herbaceous fragrance and flavor.
Planting, tending, and harvesting the agave plant remains a manual effort, largely unchanged by modern farm machinery and relying on centuries-old know-how. The men who harvest it, the jimadores, have intimate knowledge of how the plants should be cultivated, passed down from generation to generation.
By regularly trimming any quiotes(a several-meter high stalk that grows from the center of the plant), the jimadores prevent the agave from flowering and dying early, allowing it to fully ripen. The jimadores must be able to tell when each plant is ready to be harvested, and using a special knife called a coa (with a circular blade on a long pole), carefully cut away the leaves from the piña (the succulent core of the plant). If harvested too late or too early, the piñas, which can average around 150 lb in the lowlands to 240 lb in the highlands, will not have the right amount of carbohydrates for fermentation.
After harvesting the piñas are transported to ovens where they are slowly baked to break down their complex fructans into simple fructoses. Then the baked piñas are either shredded or mashed under a large stone wheel called a tahona.
The extracted agave juice is then poured into either large wooden or stainless steel vats for several days to ferment, resulting in a wort, or mosto, with low alcohol content. This wort is then distilled once to produce what is called "ordinario", and then a second time to produce clear "silver" tequila. Using at least two distillations is required by law. From there the tequila is either bottled as silver tequila or it is pumped into white oak barrels to age, where it develops a mellower flavor and amber color. Rested (reposado) must be aged for 2 months, "aged" (añejo) for 12.
Only certain mezcals, usually from the state of Oaxaca, are ever sold con gusano (with worm). They are added as a marketing gimmick and are not traditional. The tequila regulatory council does not allow scorpions to be included in tequila, although they sometimes are.