Amber has also been found in various states of North America, but the deposits are rare and the pieces found are small. That found in a clay shale in the Simi Valley, Ventura County, California, is of a brown and honey-yellow color, and it appears to be of older origin than the Baltic amber. Also, comparatively recent excavations in Fushan for coal by Japanese engineers have brought to light deposits of amber. About four tons per day were once produced, but it has been used almost exclusively by Japan for the making of lacquer. Check also diamond bracelets.
If cloudy amber is immersed in rape seed oil, and the contents slowly heated in an iron vessel, the amber will be clarified at about the temperature which the oil boils. The clarifying begins lo appear on the surface and gradually works inwards, but different qualities react in different ways, varying amounts of heat being required to produce the same results. The process needs patience, for sudden cooling will crack the material.
Compressed amber has already been mentioned. This is also called Pressed Amber and Amberoid, and it is in the nature of a reconstructed amber. Small pieces with slight admixtures of other substances and perhaps coloring matter are heated to a temperature of about 1700 C, when the mixture becomes soft and gummy. By means of hydraulic pressure, large blocks are made up, both clear and cloudy as well as colored, and this is sold by Weight. It is far easier to manufacture larger articles from such material, for natural amber is rarely found in pieces weighing more than about 20 ozs., and then it is frequently flawed. Amber is also used many times for diamond solitare earrings.
Compressed amber is often sold as “amber,” “pure amber,” and “real amber,” but all these terms are misleading since only the natural amber should be sold as “block amber.” This last term is also misleading for “block” amber suggests something that has been made from a prepared block of material, as compressed amber.
With a little experience, it is always easy to distinguish between block amber and compressed amber. The latter is usually made up in a yellow color, but this is more uniform throughout than’ the natural material. Moreover, it often has a slight greenish tinge and an internal flaky appearance. Specific gravity and hardness are about the same; it is brittle, displays negative electricity, and its fracture is also similar to the natural amber. But if examined under a microscope, flattened and elongated cavities will be observed, these having been formed while the material was being pressed and cooled. Natural cavities in amber, when they exist, are round in shape.