I’d better give the answer, since several experts are nearly correct. It is 5.0mm
Malaya garnet from East Africa is 99% orange and brown. Even with a very slight pink in East African malaya, it is still very orange. Madagascar garnets can be quite pink and still classify as malaya, but they have always been slightly orangy pink, darker tone, with visible brown.
This is an extremely pastel pyrope garnet, the most pastel, non-white garnet I’ve ever seen. The color, to my eyes, has a microscopic element of blue, making it a very slight hot pink, not an orangy pink. Again this is not typical of garnet.
Natural spinels will measure a refractive index of 1.718, and very pastel malayas, 1.750. This is singly refractive at 1.732, proving pyrope.
Pyrope garnets have higher than average dispersion, at .022, but usually the deep red color masks this. This garnet, with its pastel tone and excellent cutting angles, shows significant dispersion, with red, orange, yellow, green and blue. It is my poor man’s pink diamond.