Copal

Copal is resin from tropical trees that has hardened but has not yet turned into amber. Amber takes millions of years to form, while copal is usually somewhere between a few decades and a few thousand years old. Because it looks so like amber, it is used in jewellery and is often sold as amber. In Central America it has been burned as a sacred incense for thousands of years.

Incense and ceremony: the Maya and the Aztecs burned copal as a sacred incense and placed it in offerings. It is still burned in ceremonies in Mexico and Central America. Varnish: from the 18th century, Europeans used copal as a good raw material for varnishing furniture and carriages. In the 19th century its use on railway carriages in England and America greatly increased demand, and from 1910 New Zealand's kauri gum also went into making linoleum. Today it has largely been replaced by synthetic resins.

It has a hardness of 2 on the Mohs scale. It is soft enough to scratch with a fingernail. Its specific gravity is 1.03–1.1 g/cm³.

Its best-known localities: Sambava region, north-eastern Madagascar; Santander, Colombia; Northland, New Zealand; Zanzibar and the East African coast, Tanzania; Guerrero, Mexico.

Like amber it is very light (specific gravity about 1.06) and floats in saturated salt water, so the salt-water test does not tell copal from amber. A drop of acetone on a hidden spot makes the surface of copal sticky within 2–3 seconds and leaves a small dull mark, while amber is usually unaffected or only slightly affected. The test leaves a mark, so do not use it on valuable pieces. Over time a fine network of cracks (crazing) forms on its surface, and it cuts and crumbles easily under a blade. Its hardness is about 2, softer even than a fingernail. Copal itself is often the imitation: it may be sold as “amber”, “young amber” or “polished copal”. In Madagascar, resin collected straight from the tree is also marketed as “polished copal”.

On the “street to diamond” value ladder it sits on step 5 of nine: Ornamental stone. Copal is worth far less than amber and should always be sold clearly as copal. As an ornamental stone, its value depends on clarity, colour, size and inclusions: pieces with insects or plants attract more interest, but because these are present-day species they have less scientific importance than inclusions in amber. Surface crazing and the tendency to deteriorate over time lower its value. For copal used as incense, purity and scent are what matter.

The Maya and the Aztecs believed that the scent and white smoke of burning copal opened communication between people and the gods; copal was placed in offerings and regarded as “food of the gods”. In Aztec times copal was believed to help with toothache, a bloated stomach, bleeding and the bites of venomous animals. In Central America, farmers are recorded as burning copal as an offering to protect their fields. Some indigenous communities in Mexico and Central America still burn copal as a sacred incense in temazcal (sweat lodge) ceremonies and on Day of the Dead altars. There is no scientific evidence that copal cures toothache, stomach complaints or venomous bites; anyone bitten by a venomous animal needs medical help straight away. Like any incense, burning copal releases fine particles and volatile organic compounds into the air; incense smoke breathed often indoors is known to irritate the airways, so good ventilation is needed. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.