Tumbled amber – Sumatra, Indonesia

Indonesian amber is notable for its unique range of colors, geological age, and the rarity of its inclusions. It is among the more recently discovered sources of amber and has gained popularity in the last few decades, particularly for its rare blue and green varieties.

Origin

Indonesian amber primarily comes from the islands of Sumatra, Borneo (Kalimantan), and Sulawesi. The most famous deposits are located in the Aceh province on Sumatra. Geologically, this amber dates back to the Miocene epoch, approximately 20 to 23 million years ago.

Colors and optical properties

Indonesian amber appears in a wide spectrum of colors. The most prized is blue amber, which fluoresces with a blue glow under UV light or in direct sunlight. This effect is caused by the presence of aromatic hydrocarbons. However, the blue color does not always manifest under all conditions—it is best observed under UV light or in direct sunlight. Green amber is rarer and gets its color from trace elements and natural oxidation. Red and brown varieties are more common and resemble Baltic amber in appearance. Golden amber is translucent and features honey-yellow shades.

Composition and physical properties

Indonesian amber has a hardness of about 2 to 2.5 on the Mohs scale, making it relatively soft and easily scratched. Its density ranges between 1.05 and 1.10 g/cm³, which is why it often floats in salt water. Chemically, it contains less succinic acid than Baltic amber, setting it apart.

Inclusions

Unlike Dominican or Burmese amber, Indonesian amber very rarely contains insect inclusions. It most often contains plant remnants such as fragments of leaves, needles, or resin bubbles. Air bubbles can produce interesting optical effects. Occasionally, microorganisms appear. The geological conditions and age of this amber likely did not allow for the preservation of larger amounts of animal inclusions.

Extraction

Indonesian amber is mined by hand in tropical jungles, often within coal-bearing sediments. After extraction, it is cut, polished, and sold either in its raw form or as a crafted gemstone.

Indonesian amber is popular in Asia, Europe, and the United States. Its price depends on color, clarity, and the presence of inclusions. Blue amber is the rarest and most expensive. Green amber is also rare but more affordable. Red and golden amber are among the more common and less costly types. It is used mainly for making necklaces, bracelets, rings, and decorative items, and is often combined with silver or other precious metals.

Authenticity

There are several ways to verify the authenticity of Indonesian amber. In the salt test, amber floats in salt water with a density higher than 1.1 g/cm³. Under UV light, blue amber fluoresces blue and green amber often yellow. When heated, real amber emits a typical resinous odor. It feels warm and non-sticky to the touch, unlike plastic imitations, which tend to be cold and excessively lightweight.

There are many counterfeits on the market. Plastic imitations or pressed amber—made by compressing small fragments—are commonly sold. This type has lower value than natural amber. Another common substitute is copal, a younger natural resin that is only 1 to 5 million years old.