Microworld Gems & Gemology, Summer 2015, Vol. 51, No. 2

Amber with Mite Inclusion

John I. Koivula

Amber showing mite inclusion under shadowed transmitted and fiber-optic illumination.
Figure 1. A mite with exceptionally long front legs (2.1 mm), as seen using shadowed transmitted and fiber-optic illumination (left), was found in this small 13.15-mm-long fragment of amber (right). Images by Nathan Renfro.
A most unusual mite (figure 1, left) was discovered as an inclusion in an approximately 30-million-year-old double-polished plate of amber from the Dominican Republic (figure 1, right). The specimen was acquired from the private collection of William W. Pinch of Pittsford, New York. The plate itself weighed 0.77 ct and measured 13.15 × 7.59 × 2.76 mm, while the mite’s body was 0.34 mm in length.

What made this mite unusual was that the longest front leg measured approximately 2.10 mm, disproportionately long in relation to the rest of its body. This type of mite, of the genus Podocinum, might be awkward-looking, but its morphology has survived millions of years virtually unchanged, an indication that it was just as efficient a predator then as its living counterpart today. Podocinum is a very slow-moving mite that lives in loose soil, feeding on springtails (Collembola). As it travels about, the mite uses its extremely long front legs to explore the soil around it and quickly snare any springtail that happens to come too close.

A literature search failed to turn up any other example of a Podocinum mite as an inclusion in amber, making this an even more interesting specimen. So while a small polished piece of amber itself might have virtually no commercial or scientific value, the addition of a well-preserved microscopic organism completely changes the value factor of the specimen.

John I. Koivula is an analytical microscopist at GIA’s Carlsbad laboratory.