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EN CRACK’N OPEN GEODES ™ • GEODES • 29643-ED507-8-9Geodes-booklet-ENG.indd 1 23/06/15 09.03 Hello, Geo-Kids! Stefano Piccini ARE YOU READY TO FOLLOW MY TYRANNOSAUR BABYREX™ AND I ON OUR EXCAVATION MISSION? JOIN US ON A JOURNEY INTO THE STRANGE WORLD OF GeodES! Managing Director Geoworld Geologist & Paleontologist Dear Geo-Kids, Are you ready for an exciting journey discovering the wonders of Nature? I have been doing it for 30 years, and I assure you, this extraordinary adventure brings enthusiasm and intrigue without limit. By the end of our adventure, you will be beginning geologists! An idea of Stefano Piccini Written by Stefano Piccini Edited by Erika Iaconcig Project and graphic by Geoworld Science and Art Team Concept and supervision art by RAM All rights reserved. No part of this booklet may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, without permission in writing from the publisher. Dr. Steve Hunters® is a registered trademark owned by Geodreams S.r.l. Copyright © 2015 by GEOWORLD S.r.l. 29643-ED507-8-9Geodes-booklet-ENG.indd 2-3 23/06/15 09.03 Do you know what a Geode is? We must first start from the magma chambers... When a volcano erupts, it releases the magma that accumulated underneath it in a vast cavity known as the magma chamber. The magma is a mass of molten rocks which contain many different elements including: aluminum, magnesium, iron, sodium, potassium, calcium, silicon, and several gasses. When magma erupts from a volcano, it is known as lava. After magma and lava cool, they form igneous rocks (“igneous” is derived from the Latin, ignis, or fire), meaning “rocks formed by fire.” There are two types of igneous rocks: effusive (rocks solidified on the Earth’s crust) and intrusive (rocks solidified below the Earth’s crust). Magma does not cool and solidify in a homogenous manner (evenly). Beneath the Earth’s crust, poor heat dispersion leads to a slow solidification process. As the magma solidifies, the elements’ atoms organize in “crystalline lattices” which grow until the rock solidifies, but before the entire rock crystalizes. This is why intrusive rocks form big crystals. Some crystals are truly wonderful, multicolor and precious, like diamonds! The combination of gas bubbles and temperatures can affect the minerals dissolved in magma, creating strange objects: like geodes. When gas bubbles remain trapped in the magma, one of the most fascinating geological phenomena occurs: the formation of geodes. Volcanic stones Volcanic stones 29643-ED507-8-9Geodes-booklet-ENG.indd 4-5 Stack of small geodes 23/06/15 09.04 A geode is what remains of a gas bubble when it stays “trapped” in the magma. also occurs in the kitchen: a dense pudding drips more slowly than a liquid soup. Externally, a geode extracted from basalt or volcanic stone looks like a stony globe. An elongated geode forms when gas bubbles are trapped in quick flowing magma. If the geode is pear shaped, the pointed end indicates the direction of the magma flow. In contrast, when dense magma flows slowly over the bubbles, the geode takes on a spherical form: in some cases, even perfectly round! Incredibly, the spherical geodes look like small planets! Perhaps, this explains why they were named: in ancient Greek, the word geode means “similar to Earth.” Opening a geode can be like entering a small and wonderful world made of shiny crystal, thousands of years in the making. The word “geode” applies to both the outer rock and inner crystals. Round geodes A geode’s appearance depends on how fast the magma flowed before solidifying. BASICALLY, A GEODE IS A “SOLID” BUBBLE, OR A CAVITY INSIDE AN IGNEOUS ROCK. Geode fragments If magma flowed quickly: the geode is oval shaped. If magma flowed slowly: the geode is round shaped. The density of the magma determines its speed, the more liquid, the faster the flow. If you think about it, the same phenomenon 29643-ED507-8-9Geodes-booklet-ENG.indd 6-7 23/06/15 09.04 But, where do the crystals come from? A fter a cavity forms inside magma, water gradually seeps through the surrounding rocks. This water may come from an underground aquifer or thermal (volcanic origin) source. In any case, the water contains dissolved minerals. One such mineral, silicon, the most abundant element on Earth after oxygen, is the main component of crystalline rocks. Agata slice Silicon deposits itself into the empty space of the bubble, forming a layer on the walls (a little like limestone in an old dishwasher). Usually, the first layer is compact quartz or matte, bluish agate called chalcedony in mineralogy. Over thousands of years, crystals grow on this first layer and eventually fill the entire geode. Really, it’s a mineral version of the Easter egg! Sometimes only a few inches in diameter, but in some cases, reaching larger dimensions. JUST THINK, SOME GEODES ARE REAL CAVES (LIKE THE BIGGEST ONE EVER FOUND, CRYSTAL CAVE IN OHIO), AS DEEP AS 33 FEET! The types of crystals grown inside these amazing rock spheres vary. Amongst the most common are: quartz, zeolites, carbonates, and sulfates. Crystal formation depends on both chemical composition and fluid temperature (from 1562 to 122 Fahrenheit) of the liquid which soaks through the surrounding rock. The most beautiful geodes are contained in quartz. Okenite 29643-ED507-8-9Geodes-booklet-ENG.indd 8-9 23/06/15 09.04 Quartz is one of the most common minerals of the Earth’s crust and is frequently found in igneous rocks. Quartz is easily recognizable because it looks like a hexagonal prism. Quartz is one of the main materials used to make glass. It has many chemical and physical properties, like: durability, heat resistance, and electrical polarization. Quartz‘s characteristics lend to use for many electronic tools like quartz watches, radios, and digital instruments. Halogen bulbs and many scientific instruments (especially optics) are also made of quartz. Since ancient times, the most precious specimens are cut to create gems for jewelry. One of the most beautiful varieties of quartz found in geodes is amethyst. Amethyst is often present in volcanic rocks; accumulated in small pyramidal clusters. It is commonly used in jewelry for its brightness and characteristic purple color which comes from traces of iron. Legend has it, Amethyst was a beautiful nymph that the God Bacchus loved. Bacchus gave Amethyst his favorite color, the color of wine, as a token of his love. The geodes that contain amethysts are most valuable and, therefore, the most sought after. Another mineral that is typically present in geodes is calcite, whose crystals compose three-sided, colorless or delicately colored prisms; these have a slight fluorescence and are often grouped in extraordinary heart or butterfly-like formations! Other minerals than can appear in the form of crystals inside the geodes are pyrite, dolomite, celestite, limonite and opal. Amethyst geode Celestina geode 29643-ED507-8-9Geodes-booklet-ENG.indd 10-11 23/06/15 09.04 G eodes can be found all over the world, as expected, there are greater concentrations in volcanic areas and deserts. Rarely, geodes form in sedimentary rocks, or rocks formed slowly from an accumulation of debris, mud and other sediments. Iron, cobalt, nickel, and most frequently manganese nodules are common on the ocean floor. Many nodules contain the same multicolor characteristics of minerals found in geodes: such as agate, chalcedony and jasper. The essential difference between a nodule and a geode is that the first is totally compact, without empty spaces, while the second is hollow. The most spectacular geodes come from Brazil, but there are geode deposits in Namibia, Mexico, and other North American countries too. SUCH BEAUTIFUL GEODES WERE FOUND IN IOWA THAT THE STONE BECAME THE STATE’S SYMBOL. Similar to geodes, nodules are geological formations containing crystals. A nodule is less attractive then a geode because of its irregular shape. Basically, any mineral formation with a difference between the outside and inside composition is called a nodule. Nodules could be a mineral like pyrite wrapped in a block of carbon, or crystals surrounded by a lump of fossil sediment. 29643-ED507-8-9Geodes-booklet-ENG.indd 12-13 23/06/15 09.04 P atience is essential to keep the geode intact when opening the rocky sphere. FASCINATING, DON’T YOU THINK? NOW, IT’S YOUR TURN TO CONTINUE THE MISSION; THERE’S A NEW DISCOVERY WAITING! The bigger the pieces, the easier to admire the crystals. Ideally, you try to divide each geode in half, like a big nut, in order to preserve them in your collection. Geode section You must be ready for disappointment. Often, geodes are completely hollow with no crystals inside. Discovering an empty geode can leave a bitter expression on the face of any aspiring geologist… this has happened to me more than once! Indeed, no one knows what’s inside a geode until opening it... Therefore, it’s best to carefully hit the geode. If the geode is empty, a hard blow from a hammer could break it into dozens of pieces that fly in all directions. Insights and fun facts on : www.drs tevehunt ers.com printed in China 29643-ED507-8-9Geodes-booklet-ENG.indd 14-15 23/06/15 09.04 WONDERS OF NATURE ™ USA LLC Tucson, AZ Ph. +1.520.884.4867 [email protected] www.geoworldusa.com ASIA LTD Kowloon Bay, Hong Kong Ph. +852.3543.1890 [email protected] www.geoworld.asia www.drstevehunters.com www.geoworldgroup.com 29643-ED507-8-9Geodes-booklet-ENG.indd 16 29643 S.r.l. 33040 Torreano (UD) - Italy Ph. +39 0432 715611 [email protected] www.geoworldgroup.com 23/06/15 09.04