Biały Bursztyn photo: PB STUDIO
Adam Chętnik, a Polish amber researcher and founder of the Amber Department at the Polish Academy of Sciences’ Museum of the Earth, defined as many as ca. 200 varieties in his Mały słownik odmian bursztynu [A Small Dictionary of Amber Varieties] (1981). He systematised and described transparent and opaque amber, along with their colour variations. From red, orange, through yellow, bluish, greenish, beige, to brown, almost black and white. He wrote about dappled amber, clouded amber, gem amber and cabbage-leaf amber, enough to astonish a painter.
White amber has always been considered the most valuable because it is the rarest. Pieces of white Baltic amber are exceptionally prized by amber artists, collectors and jewellery makers alike. Since time immemorial, they have been the most highly valued. Today, unique pieces fetch prices of even several dozen Euros per gram. Jewellery with royally pure white amber, or with white amber with many, for example bluish, inclusions, always attracts the eye.
White amber has several varieties, with the rarest ones being chalk amber (chalky white) and bone amber (white amber in yellowish shades, reminiscent of ivory). The Eskimos, who are experts at naming the white shades of snow, would certainly expand this classification. The colour white is often found in amber in combination with other colours. Together, they form unique patterns: mosaics, rings, patches and stripes, etc.
White amber contains microscopic gas bubbles (0.0008-0.001mm in diameter). Their quantity can reach up to 900,000 per 1mm2 of polished surface. This constitutes even up to 50% of the piece’s volume. By comparison, opaque yellow amber has less than 25,000 of these bubbles per 1mm2 (Matuszewska, Katinas 1971, Klebs 1887). The influence of gas bubbles on colour and transparency is easiest shown with the example of an egg white. Transparent and light yellow, it changes into opaque white foam having been aerated when whisked. And white amber has the internal structure of solid foam.
The presence of air bubbles causes pieces of white amber to have a lower microhardness. It also has a direct influence on its specific weight (density). White amber can have a density lower than water, i.e. below 1g/cm3.
Where did the gas bubbles in amber come from? They probably formed when the accumulated resin was setting or are a result of chemical transformations. They can be captured air bubbles or fine water droplets. White amber varieties were usually formed inside the tree trunk: in pockets, underneath the bark, between the annual growth rings. There are very rare white varieties of drip forms created on the outside of what used to be the trunks of amber trees.
The surface of amber darkens with time. White changes into yellow and then into orange. In hundreds of years, it will not look anything like the original white. However, no expert would ever call this a defect but rather an amazing property which shows amber to be a living stone.
Source: "Bursztynnisko" Magazine