Merit Block Coal Deposits
Kapit Division, Sarawak State, Malaysia
Upper Nyalau Formation
Weight: 351.5 grams
Dimensions: 123 x 86 x 45 millimeters
The specimen arrived freshly cut from what was a larger, football-sized specimen; with a minor amount of shaping/sanding, I then polished it as best I could. This material is very soft, so a glassy polish similar to that of harder ambers isn't possible.
Borneo amber is essentially coeval in age with Sumatra amber, or at least its Formations (upper Gumai, Air Benakat, and lower Muara Enim), being Early to Middle Miocene in age. Like Sumatra amber, it is derived from a dipterocarp tree source, and is similar in color, clarity, and hardness.
Both ambers also were deposited during periods of active volcanism, and indicators are easily seen in much material (esp. Sumatra amber): light-colored, opaque "swirls" are a common sight and are actually tiny suspended droplets of congealed resin, having formed in the presence of considerable heat. Direct and indirect effects of volcanism, such as reduced light due to ash clouds, caused great stress to the resin-producing trees, and enormous quantities of resin were produced: the largest single specimen of amber in the world was uncovered in Sarawak, and weighed 68 kilograms (~150 pounds).