Optical dating is a method of determining how long ago mineral grains were last exposed to daylight. It is useful to geologists and archaeologists who want to know when a particular event occured.

Ages can be determined from a few hundred years to 100,000 years, and can be reliable when suitable methods are used and proper checks are done. Ages can be obtained outside this range, but they should be regarded with caution. The accuracy obtainable under optimum circumstances is about 5%.

The minerals that are measured are either quartz or feldspar. There are advantages and disadvantages to using each.

Crucial to the optical dating method is that there was adequite daylight exposure to the mineral grains before they were buried. Aeolian depositional environments, such as sand dunes and loess, usually satisfy this criterion. Some water-laid deposits do too.

It is essential to contact an optical dating laboratory before collecting samples for optical dating.