Olivine is usually green. It sometimes comes from space in a very colourful form in tiny spheres called chondrules in meteorites.
たいてい橄欖石 【かんらんせき】は緑です。時々隕石のコンドルールの中に色鮮やかな橄欖石が見れます。もっと詳しい情報はここ。顕微鏡のイメージはここ。
For more information see here. A microscope image may be seen here. Completed solids and nets may be viewed in Galleries → Papercraft → Crystals → Olivine, or by clicking here.
出来上がったペーパクラフトはGalleries → Papercraft → Crystals → Olivine で見れます。楽しんでください!
Enjoy!