给你一个《大英百科全书》上的介绍：AMBER:fossiltreeresinthathasachievedastablestatethroughlossofvolatileconstituentsandchemicalchangeafterburialintheground.Amberhasbeenfoundthroughouttheworld,butthelargestandmostsignificantdepositsoccuralongtheshoresoftheBalticSeainsands40,000,000to60,000,000yearsold.Amberoccursasirregularnodules,rods,ordroplikeshapesinallshadesofyellowwithnuancesoforange,brown,and,rarely,red.Milky-whiteopaquevarietiesarecalledboneamber.Theturbidityofsomeamberiscausedbyinclusionsofmanyminuteairbubbles.Manyhundredsofspeciesoffossilinsectsandplantsarefoundasinclusions.Deeplycolouredtranslucenttotransparentamberisprizedasgemmaterial.Moderninvestigativetechniquesaredirectedtowardisolatingandidentifyingasmanyaspossibleoftheindividualresincomponentsand,ultimately,toestablishingageneticrelationshipbetweenfossilresinsandmodernresin-producingtrees.Bymeansofinfraredspectroscopy,Mexican(Chiapas)amberhasbeenshowntoberelatedtoamodernleguminoustree,Hymenaea.Thoughinthepastamberwasbelievedtobecompletelyamorphous,subsequentX-raydiffractionstudieshaverevealedcrystallinecomponentsinsomefossilresins.Ornamentalcarvedobjects,beads,rosaries,cigaretteholders,andpipemouthpiecesaremadefromamber.Amberoid,or“pressedamber,”isproducedbyfusingtogethersmallpiecesofamberunderpressure.Parallelbands,orflowstructure,inamberoidhelptodistinguishitfromnaturalamber.Despitetheintroductionofnumeroussyntheticsubstitutes,thebeautyoftherealmaterialhasremainedunexcelled.建议你说明这个介绍转载于《EncyclopaediaBritannica》即《大英百科全书》。