Amber stones are not gemstones in the traditional sense. Instead, they fall into the category of organic gemstones. Just like their counterparts pearl, ivory and coral, amber forms from natural occurrences in organic matter as opposed to forming in rocks and mineral compounds. Amber crystals form through the fossilisation of tree resin. Amber resin is not the same as ordinary tree sap. This resin is sourced specifically from the pinus succinifera tree. The fossilisation of amber crystals can be traced back to the Tertiary period of time, making them at least a few million years old.
Occurrence and Mining
Amber and plastic can share many visual characteristics. They can both have a refractive index (RI) of 1.540, so an RI reading is not definitive. Therefore, the next step is likely a hot point test. This is a destructive test, but if conducted with care, it can leave no visible marks. First, find a place on your specimen where a mark would be as unobtrusive as possible (for example, on the bottom, an edge, or an area with existing scratches). Next, heat the tip of a needle until it glows red. Touch the selected spot just enough to release a tiny whiff of smoke. Now comes the hard part. Smell the smoke. If it’s genuine, it will smell like fine incense. If it’s plastic, it will smell chemical and offensive. (This is another reason to make your test on as small a scale as possible). Although amber and copal share the same RI, SG, and most other properties, copal will fluoresce whiter in shortwave ultraviolet light than amber. (Making this judgement call depends on having tested enough samples of both materials to recognize the difference).
Yellow, orange, and brown
2.0 to 2.5