Copper Dragon 22 VISIT OR GUIDE Stibnit e Stibnite is the most common of the antimon y minerals It is of ten found in groups of longbladed crystals with lengthwise striations The crystals are slightly fexible and sometimes have angular bends in them or may be twist ed along their lengths Stibnite is a low temperature mineral found in veins mineraliz ed by h ydrothermal solutions in hot spring deposits in pegmatites and in deposits where the original minerals have been replaced by other s China is home to large antimon y deposits Gift from Xu ZhengLiang East China Geological Institute Quar tz Crystal with T our maline S everal dark green tourmaline crystals grew near the base of this large quar tz crystal from Minas Gerais Brazil T ourmaline crystals vary in color with either horiz ontal bands lik e these or with concentric rings radiating from the center of the crystal outw ard Purchased b y the Society Obsidian Obsidian is v olcanic glass It forms when lava solidifes very rapidly usually when hot lava fows into a cool body of w ater lik e a lak e or a sea The lava solidifes too quic kly for minerals to form crystal structures so an amorphous glass is formed instead The mot tled pat terns of blac k and brown in this speci men from Ixtepeque V olcano Guatemala are the result of fowing lava layer s that lef t bands and streaks of color The small gray spheres are feldspar fber s cemented by silica they barely had time to form before the lava solidifed S ome obsidian also contains stone bubbles with crystals ar ranged in concentric shells inside large cavities These are lef t behind by g ases escaping from the lava Obsidian fractures in the same w ay as glass along nested sets of arcs R az or sharp edges result where the fractures inter sect These sharp edges have made obsidian a desirable mate rial for toolmaking It is also used in jewelry and ar t objects Gift from Gabriel Dengo Guatemala City Guatemala Stic htit e in Ser pentine The lilac stic htite is a rare alteration product of the green serpentine minerals that form most of this specimen Stic htite w as fr st described in 1 91 0 from the site in Dundas T asmania where this specimen w as collected It is named for R ober t Stic ht an Australian metallurgist born in the United States Gift from the Department of Geolog y Univ ersity of T ennessee Kno xville L y ons Sandst one The sand grains in this sandstone were deposited by wind in sand dunes 250 million year s ago The P ermian L yons S andstone is resistant to weathering because it is composed mostly of quar tz grains cemented by silica Most of the sandstone splits evenly along its fat bedding planes and has been widely used as a building stone in Boulder and on the Uni ver sity of Colorado Boul der campus