An online method and system for evaluating a gemstone is provided that enables a consumer to use a personal computer to evaluate the visual appearance and measurement data of the gemstone by emulating the laboratory instruments that previously collected the data for the gemstone. The computer is connected to the internet and a website that is linked to a gemstone database, emulation software and graphical user interface. The consumer identifies the specific gemstone he or she wants to evaluate, and an interactive gemstone certificate screen is displayed. The consumer separately selects and then emulates a variety of lab instruments, such as color and clarity grading, geometric measuring, and light performance and light ray tracing instruments. Graphical images and data pertaining to the selected gemstone are displayed on the computer monitor, and selected portions of the database are downloaded and saved on the computer memory.