Copal with inclusion (wikimedia commons)

Subfossil copal, which is found one or two meters below living copal trees from roots of trees that may have lived thousands of years earlier, often has inclusions and is sometimes sold as "young amber". Copal can be easily distinguished from genuine amber by its lighter citrine colour and its surface getting tacky with a drop of acetone or chloroform.

Kauri gum with inclusion (wikimedia)

Kauri gum is a subcategory of copal. It is a fossilized resin detracted from kauri trees (Agathis australis), which is made into crafts such as jewellery. Kauri forests once covered much of the North Island of New Zealand, before Māori and European settlers caused deforestation, causing several areas to revert to sand dunes, scrubs, and swamps.

Kauri gum with (wikimedia commons)

Kauri gum formed when resin from a kauri trees leaked out through fractures or cracks in the bark, hardening with the exposure to air. Lumps commonly fell to the ground and became covered with soil and forest litter, eventually fossilising. Other lumps formed as branches forked or trees were damaged, which released the resin.

Sterling silver cat amulet with amber (by DropOfAmber)

The gum varies in color depending on the condition of the original tree. It also depends on where the gum had formed and how long it had been buried. Colors range from chalky-white, through red-brown to black; the most prized is a pale gold, as it is hard and translucent. The size of each lump also varies greatly. Carbon-dating suggests the age of most kauri gum is a few thousand years.

Do not get fooled by pretty, translucent and cheap nuggets with inclusions -- most often it is copal. It tarnishes with time, cracks and dries out, loses its shine, whereas amber maintains it for a very very longtime -- it is several tens of millions years old already, so another hundred or so would not do anything to it.