Amber

Amber is an organic gem, formed when sap from ancient trees hardened and fossilised tens of millions of years ago. It is fossilised tree resin rather than a mineral, with the composition C10H16O. The material is sometimes called the gold of the North.

Amber reached a stable state after burial, when it lost its volatile components and underwent chemical change; unlike sap, it does not dissolve in water. It derives from resin-bearing trees of dense forests that no longer exist. In the living tree the resin served a protective function, sealing breaks in the bark and, through its antiseptic and sticky properties, defending against disease and burrowing insects.

Its optical and mechanical constants are modest and consistent: a refractive index of 1.540, a specific gravity of 1.08, and a Mohs hardness of 2.0 to 2.5. Hardness is reported to vary from 2 to 3 on the Mohs scale, a relative softness that suits the material to carving and working. Specific gravity lies between 1.04 and 1.10, making amber only slightly heavier than water; it floats in a saturated salt solution but not in ordinary seawater, a property that allows large beads and pendants to be worn comfortably. Amber has a melting-point range of 200 to 380 degrees Celsius, yet it tends to burn rather than melt. It is a poor conductor and feels warm in the cold; when friction is applied it becomes negatively charged and attracts light particles, and the Greek word elektron stands behind the word electricity.

Amber occurs as irregular nodules, rods or droplike shapes in all shades of yellow with orange and brown nuances, and rarely red; milky-white opaque varieties are called bone amber. Microscopic air bubbles let amber float and be carried by rivers or the sea, and white opaque Baltic amber may hold 900,000 minuscule bubbles per square millimeter. Because of those microscopic air bubbles, Baltic amber tends to appear cloudy or milky. Exposed to air, amber darkens as oxygen acts on it: a clear piece becomes yellow, a honey-coloured piece red or red-brown, and the surface progressively grows more opaque.

Succinic acid makes up 3 to 8 per cent of the structure of Baltic amber. Baltic amber, or succinite, is the most plentiful kind found in the Old World and is named for its high concentration of succinic acid. One review describes natural Baltic amber, or succinite, as the most common fossil resin on earth and one of the most common decorative stones. Because of the presence of succinic acid, Baltic and Ukrainian ambers belong to class Ia, one of the five major classes of fossil resin.

Amberoid, or pressed amber, is produced by fusing small pieces of amber under pressure, and its parallel flow bands help distinguish it from natural amber.

Most amber deposits occur in Tertiary-period sediments of Eocene age, with fewer in the Oligocene and Miocene and fewer still later. Baltic amber comes from early Tertiary beds of the Upper Eocene to Lower Oligocene around the shores of today's Lithuania, Latvia, Kaliningrad, Poland, Sweden, Germany and Denmark. It is never found in its original stratigraphic position, having been redeposited in Eocene glauconitic marine sediments as well as Neogene fluvial and glacigenic deposits.

In this type of fossilisation the organism is entrapped in a biologically inert environment and preserved as a whole, so intact insects are often found in amber. Amber containing larger animals such as scorpions, snails, frogs and lizards can be very valuable, especially when the inclusions are preserved intact. A thousand extinct animal species, as well as various types of plant matter, have been identified in amber.

Baltic amber constitutes the largest known deposit of fossil plant resin and the richest repository of fossil insects of any age. Succinite occurs in the Gdańsk Delta, where the world's largest amber mine, Primorskoje, is located, and deposits also occur in Poland, Ukraine and Central Germany. In antiquity most Baltic amber was harvested from beaches and shallow waters after autumn storms, and only in the early modern period did mining begin.

Using microphotography and CT scans, scientists obtained a three-dimensional look inside the ancient feathers and found a thin shaft without the spongy material of modern plumage.

The UCMP amber collection is one of the largest in the country, with specimens primarily from the Baltic region, the Dominican Republic, Alaska, the Philippines and Mexico. Its holdings include 2,480 databased specimens and constitute the largest institutional Chiapas collection in the United States. Since 2018 the IMLS team has resin-embedded 1411 type and non-type amber pieces and is imaging the inclusions with a digital microscope.

The most precious specimens are holotypes, the specimens on which species new to science were described, and the collection holds over 50 descriptive types including dipterans, beetles and dragonflies. Nearly 3000 pieces of amber have been digitised for the first time and made available on the Museum's Data Portal as part of the NHM Unlocked programme.

Industrial extraction from the nineteenth century onwards yielded huge amounts, estimated at up to a million pounds a year dug from the blue earth layer of the Samland peninsula in the early twentieth century.

Gdańsk deserves the title of the World Capital of Amber, where jewellery and utensils of amber have been produced for centuries. The Palanga Amber Museum, a branch of the Lithuanian National Museum of Art, was established in 1963 and is housed on the estate of Count Feliksas Tiskevicius, built in 1897 by the architect Franc Schwechten.

Although the film Jurassic Park is fiction, scientists have extracted DNA from insects enclosed in 120-million-year-old amber. Most biologists agree that the Jurassic Park scenario is impossible, since blood carried by an insect would deteriorate rapidly and be contaminated.

Raw and worked amber found around the Mediterranean and farther afield, on the Iberian peninsula, in Mesopotamia, in Anatolia, at Ugarit and in Egypt, attests to its value and transmission from the Bronze Age onwards.

Paul Getty Museum collection of amber antiquities was formed between 1971 and 1984: apart from the Roman Head of Medusa acquired in 1971 with a larger purchase of antiquities, the other ancient amber objects came as gifts.

Pliny saw the ants, gnats and lizards visible inside transparent amber as proof that amber was originally a liquid, since these creatures must have adhered to it while it was soft and remained enclosed when it hardened.

In the myth the Heliades, sisters of Phaethon, were changed into poplars whose tears fell as drops of amber into the river, to be borne off to adorn young wives in Rome. In the Greek story told by many poets, those tears on the banks of the river Eridanus were called electrum, after the Sun, which was called elector.

Amber's value turns on colour and clarity: rare pieces can be blue or green, inclusions make a piece far more valuable. Buyers should be wary of perfect-looking insect inclusions, because the insects in genuine amber are millions of years old and imitations with modern insects are very common.

Besides beads, carvings and cabochons, amber has been used for cups, bowls, snuff boxes and umbrella handles.

The Natural History Museum of Los Angeles County holds amber-encased dinosaur feathers from more than 100 million years ago, which its Dinosaur Institute researchers studied. Flies preserved in amber forty million years ago while in the act of copulation are among the treasures that will come to a proposed collections and research centre, the Natural History Museum has said.

• Upper Carboniferous, about 320 million years ago
  Oldest amber
  The earliest known amber dates to this period.
• Palaeolithic era
  Amber reaches cave dwellings
  Rough pieces reached cave dwellings in Britain and northern Europe far from any amber source. ^{18The Ancient Transport of Amber · J. Paul Getty Museum (Ancient Carved Ambers in the J. Paul Getty Museum) ↗}
• mid-second millennium B.C.
  Defined long-distance amber trade begins
  The start of organized long-distance exchange in amber.
• seventh to fourth centuries B.C.
  Pre-Roman jewelry
  The Getty collection includes pre-Roman amber jewelry of this span.
• third century BCE
  River Eridanus of amber myth
  The river Eridanus of amber myth was thought to have become a constellation.
• first century A.D.
  No literary evidence of direct trade
  There is no literary evidence of direct trade between Italy and the north until this time. ^{18The Ancient Transport of Amber · J. Paul Getty Museum (Ancient Carved Ambers in the J. Paul Getty Museum) ↗}
• 1716
  Amber Room gift to Peter the Great
  The Amber Room was given to Peter the Great.
• 1897
  Palanga estate built
  The Palanga estate was built by Franc Schwechten.
• 1963
  Palanga Amber Museum established
  The Palanga Amber Museum was established.
• 1971
  Roman Head of Medusa acquired
  The J. Paul Getty Museum acquired the Roman Head of Medusa. ^{19Amber and the Ancient World · J. Paul Getty Museum (Ancient Carved Ambers in the J. Paul Getty Museum) ↗}
• 1971 to 1984
  Getty amber antiquities collection formed
  The Getty's collection of amber antiquities was formed across this period. ^{19Amber and the Ancient World · J. Paul Getty Museum (Ancient Carved Ambers in the J. Paul Getty Museum) ↗}
• 2018
  IMLS team begins resin-embedding and imaging
  An IMLS team began resin-embedding and imaging work.