Calcite Cavern Crystals 46 VISIT OR GUIDE Pyr it e with Quar tz T in y quar tz crystals scat tered pyrite crystals and a few larger quar tz crystals encrust this specimen Pyrite is a minor ore of iron and is the most widespread and abundant of the sulfde minerals It occur s in man y kinds of igneous metamorphic and sedimentary roc ks Calcit e Ca v er n Crystals The yellowish exterior surface of this specimen is typical of calcite that forms from slowly dripping solutions in limestone caves Its interior shows coar se white crystals of calcite growing outw ard from a central core This specimen is from Crystal Cave P ennington County S outh Dakota Gift from the Geolog y Museum Colorado School of Mines Septar ian Concr etion Man y concretions or mineral masses form a r o u n d a piece of shell bone wood or other org anic material The org anic mat ter causes c hemical reactions that help concentrate and precipitate cer tain minerals from the w ater contained in the pore spaces be tween sediment grains S eptarian concretions are common in fnegrained sediments deposited in marine set tings The concretions are cut by inter secting crac ks flled by calcite siderite or other minerals The concretions may begin as a gelatinous mass that hardens fr st on the outside then crac ks as the core of the mass loses w ater Chrysotile Asbest os Asbestos is a commercial term for a group of silicate minerals that readily separate into thin strong fber s that are fexible heat resistant and c hemi cally iner t Once widely used in a variety of industrial products it is now rarely used commercially because asbestos has been found to be carcinogenic Bar it eCr est ed Blades Barite the mineral that cements deser t roses is the principal ore of barium It is a sof t heavy nonmetallic mineral that gets its name from the Greek barys heavy It is used in drilling muds where its weight helps prevent blowouts from high pressure in drillholes It is also used to mak e glass and paint as a fller for paper and textiles in cosmetics and in medicine Oncolit e Oncolites are rounded structures with concentric internal bands formed by the addition of org anic or mineral material around a core This specimen collected in S evier County Utah from the P aleocene lower Flagstaf f F ormation formed from the gradual buildup of layer s of alg ae around a snail shell that is now fossiliz ed at the oncolite s center The alg ae li ved in an ancient lak e but the snail itself w as a land snail that apparently w ashed into the lak e from a stream or a food T oday this type of snail is found only in w armer tropical climates The bands in the oncolite are formed from calcium carbon ate produced by the life processes of the alg ae They also contain silt that w as