Organic gemstones

By Magna. Correct answers are all gemstones that have plant and/or animal origins.

(3/-1) In an effort to deter poaching, Richard Leakey helped Kenya organize the public burning of 12 tons of this material in 1989.8202
(6/-2) This precursor to lignite coal shares its name with a type of aircraft, a fast-moving stream of air or water, and a shade of black.7914
(9/-3) "Electricity" derives its name from the Greek word for this gem, whose name is also one of the three colors of an electric traffic signal.66612
(12/-4) In ancient times, this red gemstone was an important commodity in the trade between countries of the Mediterranean, where most of it was harvested, and India.101757
(15/-5) Also called mother-of-pearl, this material's five-letter name is an anagram of a type of waterbird.58224

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