The tequila expression usually described as crystal clear because it is filtered after aging is cristalino.
Cristalino is a modern tequila style made by aging tequila, commonly añejo or extra añejo, and then filtering it to remove much of the color produced by barrel maturation. The result combines a clear appearance with some characteristics associated with aged tequila, such as oak-derived aromas and flavors.
Cristalino is not one of the core legal classes in the same way as blanco, reposado, añejo, and extra añejo. It is generally used as a market and production description for a filtered aged tequila. Exact methods vary by producer, including the filtration material and the length and type of aging beforehand.
A clear bottle is therefore not automatically blanco tequila. Blanco is normally unaged or rested only briefly, whereas cristalino may have spent substantial time in wood before clarification. The appearance alone does not reveal the full production history.