PRECIOUS ROCKS GEMS & MINERALS A fabulous collection of rocks, gems and minerals, gathered from all over the earth.
The world s most beautiful rocks, gems and minerals for you to treasure A collection to share with all the family Authentic pieces gathered by our specialists from all corners of the earth. Opal BRAZIL Obsidian UNITED STATES Hornblende CHINA Full-size samples Wonderful variety Spectacular display Chyrsoprase AUSTRALIA Aragonite MOROCCO Lapis lazuli AFGHANISTAN Items shown may change due to circumstances beyond our control
Don t miss out on this unique collection! FREE display box for your collection with issue 2. The most fascinating rocks, gems and minerals of our planet, including amethyst, rose quartz, agate and tiger s eye. Learn how to identify them, how they were formed and where to find them in every issue of your magazine, and in the comprehensive A-Z cards that accompany the collection.. Protect your precious collection in exclusive and specially designed display boxes. Since it was founded in 1888, this scientific and educational not-for-profit organisation has supported more than 9,000 explorations and research projects, contributing to our knowledge of land, sea and space. Items shown may change due to circumstances beyond our control
Amazing minerals MAGNETITE Did you know? A mineral is a natural substance, found on the surface or within the layers of the earth s crust. ICELAND SPAR This mineral has amazing optical properties. Looking through it is like having double vision. According to legend, a Greek shepherd discovered this mineral when he noticed the nails in his sandals were sticking to the rocks. It is a natural magnet that attracts iron. DESERT ROSE In dry conditions, gypsum crystals grow so that they resemble petals. These beautiful formations are like blossoms set in stone. CALCITE Used by the Romans to make cement, this mineral dissolves in acidic water and forms stalactites and stalagmites in caves. PYRITE This form of iron sulphide is sometimes called fool s gold, due to the way it sparkles and glistens. FUCHSITE This form of muscovite, or common mica, owes its intense green colour to the chromium oxide it contains. It is often found alongside emeralds.
and stunning gemstones Did you know? A gem or precious stone is a rock or mineral that can be cut and polished to use in jewellery making or arts and crafts. Man-made versions are created with resins and pigments. TIGER S EYE A variety of quartz with a unique appearance, this gemstone is distinctive due to its beautiful layers of colour and characteristic sheen. AMAZONITE Also known as the stone of the Amazon, this rare mineral s rich blue-green colour has made it highly valued by collectors. AMETHYST This purple crystalline mineral is a soughtafter variety of quartz and has been used as a gem for centuries. LAPIS LAZULI CHALCEDONY GEODE Formed inside cavities in rocks, these are like miniature crystal caves and highly prized in collections. The quality of this aggregate of different minerals is dependent on the proportion of lazurite, which produces the intense blue colour. BLUE AGATE Playing an important role in Buddhism, and in Feng-Shui, this stone is said to represent purity, innocence and integrity. EMERALD One of the most sought-after precious stones, this is a variety of beryl. It owes its green hue to the chromium or vanadium within it.
Everything you need to know about the world of precious rocks, gems and minerals Discover why the world of geology has fascinated man since the dawn of time, with these fact-packed magazines and A-Z reference cards, developed by experts and designed for the whole family to use. YOUR MAGAZINE SECTIONS MINERALS GEMS PLANET EARTH MINERALS AND MAN AROUND THE WORLD COLLECTING GUIDE TO MINERALS PLANET EARTH Plate tectonics: in constant motion The outermost part of the Earth (its crust) consists of a series of rigid plates that are in constant movement. This movement is almost imperceptible to us, ranging from about 2 to 6 cm a year. Although this movement may seem insignificant, over millions of years continental masses can split and may become separated by thousands of kilometres. T he theory of plate tectonics was developed by a number of people at the end of the 1960s and in the early 1970s. It explains most of the geological processes that take place on Earth. The development of the oceans and continents, the location and types of volcanoes and earthquakes, the formation of mountain ranges or places where there is sedimentation are all processes explained by this theory. According to the theory of plate tectonics, the Earth is divided into rigid plates which move on top of another, more fluid, layer called the asthenosphere, or upper mantle. The plates vary greatly in thickness, from a few kilometres in parts of the ocean basins to up to 20 km beneath large mountain ranges. As the plates move some pull apart, whereas others collide. Still more move sideways, sliding past one another. Extremes of height and depth Diagram comparing the height of the Himalayas with the depth of the Marianas Trench 11.022 m 8.850 m Sea level 5 2 5 1 Plates separate: oceanic ridges Where plates pull apart beneath the ocean submarine mountain ranges form. Running down the centre of these ranges are deep fissures through which magma continuously flows. As this magma hardens it forms new rock, which is added to the separating edges of the plates. 2 Plates move sideways: transform faults There are places where plates neither collide nor separate, but instead move sideways past each other. These places are called transform faults. Most transform faults occur beneath the ocean s surface. The fault between the Iberian Peninsula and north Africa is of this type. 4 Hot spots Sometimes hot material rises from the centre of the Earth and raises the temperature of the underside of a plate, producing magma. This process leads to volcanic activity both on land and beneath the ocean. Oceanic trenches In places where one oceanic plate sinks beneath another plate (subduction), trenches form. These trenches may reach depths of more than 10 km. 1 4 Plate tectonics: in constant motion 45 3 Plates collide: collision of two continental plates When two continental plates collide they thicken at their edges, creating huge mountain ranges. The Himalayas was formed in this way. Here, the thickened crust prevents magma from reaching the surface. Instead, it cools within the newly created mountain chain. 3 Plumes Beneath the oceanic ridges columns of magma called plumes emerge from great depths. These spill out to form the underwater mountain ranges of the ridges themselves and in places break through the surface of the sea to form volcanic islands, such as Iceland. 4 Plates collide: collision of two oceanic plates When most plates collide, one sinks beneath the other in a process called subduction. As it sinks it melts and the magma generated rises to the surface, where it erupts from volcanoes. Where subduction occurs beneath the ocean island chains are created by these volcanoes, marking the boundary. The Japanese archipelago and the Philippines are both examples of this kind of volcanic island chain. 5 Plates collide: collision of a continental and an oceanic plate Oceanic plates are thinner and more dense than continental plates. When the two collide, the oceanic plate is subducted. The magma produced by this process rises through the continental plate forming mountains and volcanoes. The Andes was formed by this type of collision. 3 MAGAZINE BlUE agate class Oxides and hydroxides System Trigonal crystal Hardness 7 Fracture Conchoidal Exfoliation None lustre Vitreous Streak White 4 1 2 5 Blue agate SiO 2 lue agate, a sub-variety of Bquartz, is a very attractive gem with concentric bands alternately coloured blue and white. Its beauty depends on both the intensity and the extent of its blue colour. Blue agate forms in volcanic rocks infiltrated by hot silica (SiO2) solutions. Variations in the dissolved impurities and the conditions in which the minerals are deposited give rise to the different layers. If the solution cools slowly, quartz macrocrystals can form in the central section. If cooling is rapid, however, the crystals that form are microscopic. n artificial colour Many of the blue agates offered for sale to collectors are artificially coloured, having been impregnated in a vacuum with a blue dye solution. This solution penetrates the network of quartz microcrystals to a lesser or greater extent according to the porosity of the 3 mineral bands. The best way of distinguishing natural agates from treated ones is to examine the uniformity and clarity of their blue colouring, as both of these properties are better defined in natural agates. n THE BUDDHIST MInERal Nowadays, agate (particularly blue agate) is highly prized in China and India, owing to the importance of the stone in Buddhism and its role in feng shui. In the West, blue agate was a much sought-after gem during the Renaissance. This period gave rise to the majority of blue agate cameos, which were extremely finely cut. Due to their great beauty and historic importance they remain highly valuable today. Where it is found: The most outstanding pieces of blue agate come from mines in Asia, Africa and the Americas, specifically: 1. Brazil (Minas Gerais), 2. Uruguay (Artigas), 3. China (Tibet), 4. Mexico (Chihuahua), and 5. Democratic Republic of Congo. CARDS onyx.indd 2 6/9/10 12:42:12