Please refer to the link for my advice on terminology.

People sometimes have oversimplified ideas about the brine test. They think that a material that sinks is plastic, and that which floats is amber. The variables are more complicated.

Among plastics, phenolic plastics will sink in a brine (like a rock)—because their specific gravity is high. However old Celluloid also sinks in brine; but few other plastics will sink. Many thermolabile (meltable) plastics will float in brine. Some will even float in plain water (which amber will not).

The majority of semi-realistic amber imitations, since 1926, have been cast phenolics—and the brine test can be used to determine this quickly for a large number of imitations. I don't believe any phenolic plastics will float in brine.

Nevertheless, as I demonstrated in my 1976 article on amber beads, some imitations—including those from West Africa—are made from soft thermolabile plastics that float in brine. For me, these are visually recognizable. But, when in doubt, I would hot-point test them. The odor produced is a sticky-sweet plastic smell, and the material melts easily and may "spin a thread." Other plastics have aromas typical of their types. For instance, acrylic is fruity.

I recommend my Group, Amber Forever, for more thorough information about testing amber and "amber."

Be well. Jamey