The internal structure and colour of primary varieties of amber is subject to change dependent on air, humidity and light levels and other weathering processes which can turn it from yellow to redo r orange. Changes in its internal structure lead to the appearance of numerous cracks within any given piece, resulting in what is referred to as a sugar-crystal structure. Weathered amber is also covered by a "cortex" or "crust" making its surface coarse or uneven. The greatest degree of weathering is displayed by amber which has lain in deposits above the surface of the water table for a prolonged period of time. Similarly, pieces of amber which make up part of an old collection, or those which have been exposed to the effects of light, as is often the case with display items, change color from yellow to red and orange, or from white to yellowish.
In the drainage-basin of the River Narew, where the tradition of collecting and working amber goes back to the fifteenth century, a wide-ranging terminology is used to describe amber, taking into account its color and level of translucence. In his Pocket Dictionary of Polish Amber Varieties, author A. Chetnick brings together eighty names for varieties of amber, which refer not only to their color and translucence, but also to the character of their surfaces, their degree of weathering, provenance and even their suitability for working and their role in folk rituals.
Chetnick makes the following distinctions between varieties of transparent amber: gems- entirely transparent, pale yellow amber; flames- reddish amber whose colour is reminiscent of fire; honey- honey-coloured amber; clouded- amber which has concentrations of opaque areas which resemble clouds in a clear sky.
Translucent amber includes nebular and woolly varities in which the opaque sections appear in strips or concentrations reminiscent of fluffy clouds or strands of wool.
Varieties of yellow, opaque amber include beige amber- a reference to its colour- and cabbage-leaf amber- where pale yellow or white streaks appear distributed on a darker yellow background giving the effect of veins on a cabbage leaf; patchy amber- in which different shades of yellow or white form distinct patches of colour; marble and mosaic amber- where multicolored portions are arranged in patterns resembling marble or mosiaics; and finally mixed amber which consists of several varieties rolled into one piece. Grainy and striped amber is a name given when sections of various colours and degrees of translucence form stripes or rings which resemble the grain of wood.
Opaque, white varieties include chalky amber- chalky white in colour; bone amber- predominantly white with hint of yellow; giving it the appearance of ivory; and unique specimens of blue amber. These contain such a large amount of air bubbles that seen under an electron microscope, they have the appearance of solid foam.
Amber belonging to the earth category, i.e. that which has been contaminated by plant matter, is divided into the following varieties: dappled- containing small particles of grey of black plant detritus; transparent earth amber- containing detritus particles and large, single air bubbles which are clearly visible against a transparent, yellowish-brown background; green amber, which has a greenish hue; and mixed earth amber- which contains fragments of opaque, yellow amber contaminated with interspersed plant matter.
Sugar-crystal amber, so-called because of its granular appearance and red amber, are easily distinguished amongst the secondary varieties of this mineral.
:: Examples of Baltic Amber to Identify ::
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