amnh.org/mineralsgems/educators

Educator’s Guide

Harry Frank Guggenheim Hall of Minerals Morgan Memorial

Hall of Gems

• Suggestions to Help You Come Prepared

• Essential Questions for Student Inquiry

• Strategies for Teaching in the Hall

• Map of the Exhibition

• Online Resources

• Correlation to Standards

• Glossary

Inside:

• Hardness is the degree of resistance to being scratched. It’s determined by rubbing substances of known hardness against minerals and calibrating the results on the Mohs Scale. Diamond, the hardest mineral, is 10 on the scale, while quartz is 7 and talc is 1.

• Fracture and cleavage describe the way minerals break apart. Fracture is the tendency to break along rough or curved surfaces, while cleavage is the tendency to break along planes of weakness. Cleavage can help identify crystal symmetry, which can be useful in telling similar-looking minerals apart.

The properties of minerals determine how we can use them. For example, diamond and corundum (ruby) are used as abrasives because they’re very hard, while soft and slippery graphite and molybdenite can be lubricants.

How do minerals form? Minerals form when elements crystallize and/or react chemically with each other in response to environmental conditions such as changing pres-sure and temperature. They grow by adding layers to a starting point or surface, and well-formed crystals most commonly grow in an open space in the presence of a fluid. Minerals form everywhere on Earth — from thousands of meters deep to its surface and atmosphere — over time frames ranging from seconds to millions of years. The conditions under which they formed tell geologists important things about the planet. For example, jadeite jade probably formed at high pressure where oceanic crust was pushed beneath continental crust, while many rubies were forged where continents collided to create mountain chains.

Why are minerals important?Studying rocks and minerals helps us understand the greater physical world, including Earth’s history and dynamics. By analyzing a rock’s mineral content and texture, scientists can learn about the conditions at which it formed. Earth materials are resources. We rely on minerals found in Earth for many products, including metals, ceramics, fillers, semiconductors, glass, and fertilizer. Minerals are also a source of nutrients that all living things require.

What is a mineral?A mineral is a naturally occurring crystalline solid. Crystals are orderly arrangements of atoms. Minerals are the building blocks of rocks, which make up most of the planet. Some minerals, like gold and silver, consist of essentially just one element, while others combine two or more. Minerals are classified by their chemical compositions, which are defined by formulas and by the way the atoms of those chemical elements are arranged into crystals. For example, Si0

2

is the formula for quartz, in which atoms of silicon and oxygen are arranged in a precise geometry. Gems are minerals that are beautiful, rare, and durable, and which have been cut and/or polished to enhance their beauty.

What are the properties of minerals?The physical properties of minerals are determined by their chemical composition and crystal structure. Scientists magnify, crush, illuminate, scratch, and break specimens in order to determine these properties.

• Luster is the way a mineral’s surface interacts with light — how brilliant or dull it appears, for example. Lusters are either metallic (like pyrite) or non-metallic (examples include talc, which is pearly; quartz, which is glassy; and sulfur, which is earthy). Some minerals (like graphite) fall in between and are called submetallic.

• Scientists crush a mineral by swiping it across a ceramic “streak plate” to reveal the color of its powder — its streak. This can help distinguish between minerals with the same color but different streak, like hematite and magnetite.

QuestionsESSENTIAL

quartz (Si02)

jadeite (NaAlSi2O

6)

metallic:pyrite (FeS

2)

non-metallic:talc (Mg

3Si

4O

10(OH)

2)

submetallic:graphite (C)

COME PREPARED

CORRELATIONS TO THE NEXT GENERATION SCIENCE STANDARDS

Plan your visit. For information about reserva-tions, transportation, and lunchrooms, visit amnh.org/plan-your-visit.

Read the Essential Questions in this guide to see how the themes in these two halls connect to your curriculum. Identify the key points that you’d like your students to learn.

Review the Teaching in the Hall sections of this guide for an advance look at the specimens that you and your class will be encountering.

Download activities and student worksheets at amnh.org/mineralsgems/educators. Designed for use before, during, and after your visit, these activities focus on themes that correlate to the standards.

Decide how your students will explore the halls.

• You and your chaperones can facilitate the visit using the Teaching in the Hall sections.

• Students can use the student worksheets to explore the halls on their own or in small groups.

• Students, individually or in groups, can use copies of the map to choose their own paths.

Science Practices • Asking questions • Developing and using models • Planning and carrying out investigations • Analyzing and interpreting data • Using mathematics and computational thinking • Constructing explanations • Engaging in argument from evidence • Obtaining, evaluating, and communicating information

Crosscutting Concepts • Patterns • Cause and effect: mechanism and explanation • Scale, proportion, and quantity • Systems and system models • Energy and matter: flows, cycles, and conservation • Structure and function • Stability and change

Disciplinary Core Ideas • PS1.A: Structure and Properties of Matter • PS1.B: Chemical Reactions • ESS2.A: Earth Materials and Systems • ESS2.B: Plate Tectonics and Large-Scale System Interactions • ESS3.A: Natural Resources

GLOSSARYcrystal: a naturally occurring, symmetrical solid with flat surfaces, like a cube, a prism, or even a snowflake. Crystals are made of atoms arranged in an orderly, repeating pattern.

deposit: an accumulation or concentration of minerals laid down by a natural process, such as gravity or the movement of water, wind, or ice

element (chemical element): matter composed of a single type of atom. Few elements are found in an uncompounded, pure form. The periodic table is the classification of the chemical elements.

gem: a mineral that has been cut and/or polished to enhance its beauty

magma: molten rock (formed below Earth’s surface). Magma that reaches the surface is called lava.

mineral: a natural solid with a crystal structure and a specific chemical composition

mineralogy: the study of minerals, or what mineralogists — including crystallographers, mineral physicists, and crystal chemists — do

Mohs Scale of Hardness: a system for determining the resistance of a mineral to being scratched, with 1 being the softest (talc) and 10 the hardest (diamond)

rock: a naturally occurring solid made of one or more minerals. Rocks make up most of Earth’s crust.

sediments: small fragments of mineral or rock that are broken off, carried, and deposited by wind, water, or ice

vein: a distinct body of crystallized minerals that occupies a fissure within a rock mass

barite (BaSO4)

diamond (C)

gold and quartz vein in metamorphic rock

Teaching in the HALL

1d. Optical properties of minerals: Color is an important optical characteristic, but can vary within mineral types and overlap across others. Streak — the color of the residue left when the mineral is scraped against a rough surface — can help distinguish minerals from one another. Draw students’ attention to hematite (#48). Like many minerals, it is black, but its streak is distinctly red. Pyrite (#44) is gold, but its streak is black.

Luster is another optical property. Minerals can display either a metallic luster (#32-36) or non-metallic luster (remaining specimens in the left-hand case). The way light passes through some minerals can also help with identification.

Show students the halite and calcite specimens (#73, 74), and draw their attention to the mounting brackets. How do they look different when viewed through the calcite sample? (The calcite sample shows double refraction of the light passing through it, making it appear that the bracket has double bars.)

1a. Atoms, space lattices, and crystals: A mineral’s characteristic crystal structure is determined by how its atoms fit together. Have students compare the models in the center of the case to the crystal shapes of mineral specimens to the right. Ask them to explore how atomic arrangements in different minerals are expressed in actual crystals, and how bonded groups repeat in three dimensions to make crystals.

1b. Physical properties of minerals: These different crystal structures result in a huge variety of physical properties — even when minerals are made of the same element or elements. Have students compare two carbon-based minerals, diamond and graphite. How do their crystal structures and physical properties differ? (In diamonds, atoms are closely packed in all directions, making it very hard. Graphite’s atoms are closely packed along one plane only, which makes it softer.) Have students explore a variety of characteristic properties (hardness, cleavage, fracture, tenacity, specific gravity) by reading the labels and observing the samples to the right.

1c. Chemical properties of minerals: These properties reflect the chemical elements that minerals are made of. Scientists use chemical tests to distinguish between minerals with similar physical properties. They determine how minerals react under different conditions, such as exposure to heat, water, or acids. Have students explore different ways to identify minerals with chemical tests. Point out that halite (large specimen on the left) and

calcite (#12) share many physical properties, but halite dissolves in water and calcite in hydrochloric acid.

Scientists perform a range of measurements to determine the crystal structure of minerals, as well as their physical, chemical, and optical properties. Some minerals are easy to identify, but most require multiple tests. In this section, students will explore four cases to see how mineral properties can be determined and measured.

This hall presents hundreds of striking specimens collected from around the world. Almost everything on display came out of Earth looking the way it does here. The guided explorations below are designed around two sections of the hall: Properties of Minerals and Mineral Forming Environment. The numbers correspond to stops on the map.

PROPERTIES OF MINERALS

HARRY FRANK GUGGENHEIM HALL OF MINERALS

diamond

graphite

minerals with a metallic luster (#32-36)

streak plates show the colors of various mineral powders (#42-51)

halite (NaCl) calcite (CaCO3)

2e. Hydrothermal and metamorphic environment: Certain minerals result when two different environments overlap.Have students explore what minerals formed under these conditions near New York City. Point out different specimens such as copper (#15), pyrite (#20), and magnetite (#38).

AT OR NEAR EARTH’S SURFACE

When minerals crystalize in surface water:

2f. Evaporite environment: Lakes in warm and dry climates may contain water with a high mineral content because elements dissolved from surrounding rock formations wash into them. As the water evaporates, the concentration of dissolved elements becomes so high that they crystalize into minerals. Draw students’ attention to halite (#1, 6) and gypsum (#13).

When minerals form in igneous rocks at the surface:

2g. Volcanic environment: When lava erupts onto Earth’s surface, it typically forms mineral crystals as it cools and hardens. In addition, secondary minerals often grow in the numerous pockets and holes that form in the rock when it cools. (All of the minerals in the first volcanic case are from a basaltic rock 20 miles west of New York City.) Minerals are also often deposited around active volcanoes. For example, sulfur (#4 in the right-hand case), crystallizes from escaping sulfur dioxide and hydrogen sulfide gases. Show students hematite (#2) and calcite (#18).

When minerals form in flowing water:

2h. Sedimentary environment: Water and wind weather surface rock and mineral materials into small-er pieces, which are then transported and deposited at new sites. When these sediments react chemically with water, new minerals develop. Heavier minerals like gold will sink, separate, and concentrate, forming a placer deposit. In the left-hand sedimentary case, have students look at gold (#3, 10) and zircon (#6, 13); in the center, sulfur (#7) and calcite (#10); and on the right, hematite (#15), pyrite (#20), and magnetite (#24).

WITHIN EARTH

When minerals form from other minerals:

2a. Metamorphic environment: Conditions of high temperature, high pressure, or both can rearrange the atomic structures of minerals within rocks, transforming them into other minerals. In this environment, the minerals never become a liquid. Point out minerals that formed in this way, such as pyrite (#9, 27), talc (#13), and graphite (#18).

When minerals form in igneous rock deep in Earth:

2b. Magmatic environment: Mineral crystals grow as magma cools and hardens into solid rock. The particu-lar minerals depend on the chemical composition of the magma, its depth, and the temperature when it crystallizes. Students can observe minerals that make up gabbro rock (#11, on left), rich in calcium and magnesium, which form at higher temperatures. Minerals that make up granite rock (#3, on right), rich in silicon and aluminum, form at lower temperatures.

2c. Pegmatite environment: When magma becomes almost entirely crystalized, rare crystals can form and grow to large sizes. This happens because certain elements normally in lower abundance become con-centrated, and also because volatile components build up. The volatiles create vapor pockets that allow larger crystals to form. Point out quartz (#9, 10, 14 in the first case); zircon (#8 in the second case), magnetite (#15), and hematite (#33); beryl (#10-12 in the third case) and rose quartz (#17); and stunning examples of topaz (#3) and beryl (#8) in the last case of large crystals.

When metals are deposited in rocks:

2d. Hydrothermal environment: As water with high concentrations of metals moves through rock, it can leave rich deposits. This creates veins containing met-als such as gold, copper, and zinc, both deep in Earth’s crust and closer to its surface. Hotter temperatures at greater depth result in certain types of deposits, like pyrite (#16 in hypothermal, #25 in mesothermal), while shallower, cooler temperatures (epithermal case) result in deposits of gold (#2) and silver (#21).

Minerals are the building blocks of rocks, and form as rocks form. Mineral crystals are typically small, but sometimes grow to large sizes. In this section, students will explore minerals that form in different environments within Earth as well as at or near its surface, and see, for example, that the same mineral may form in different environments. Specimens that may be familiar to students, such as those found on the NYS Earth Science Reference Tables, are indicated at each stop.

MINERAL FORMING ENVIRONMENTS

copper (Cu)

Photo CreditsCREDITSCover: Guggenheim Hall of Minerals, gems, zircon, © AMNH/R.Mickens; prehnite, ©AMNH/C.Chesek. Essential Questions: all photos, © AMNH. Glossary: all photos, © AMNH. Come Prepared: peridot crystal, © AMNH. Teaching in the Exhibition (Minerals): all photos, © AMNH/C.Chesek. Online Resources: Earth OLogy, © Eric Hamilton; malachite, George Harlow, zircon expedition, © AMNH; gold, © AMNH/J.Beckett. Teaching in the Exhibition (Gems): all photos, © AMNH/C.Chesek.

Funding for the Educator’s Guide has been provided through the generous support of The Louis Calder Foundation.

© 2013 American Museum of Natural History. All rights reserved.

ResourcesONLINE

FROM THE MUSEUM

In Glittering Gems, Reading Earth’s Storynyti.ms/11fzxNbThis New York Times article explains what gems tell geologists about the history of our planet.

Mineralogy 4 Kids mineralogy4kids.orgDeveloped by the Mineralogical Society of America, this site includes sections on minerals in the home; mineral groups, properties, and identification; and lots of games.

Mineral Matters sdnhm.org/archive/kids/minerals This San Diego Natural History Museum site for kids explains how to identify minerals, build a collection, and grow crystals. Includes mineral FAQs and games.

Smithsonian Minerals Collectioncollections.mnh.si.edu/search/msA searchable photographic database of 100 mineral specimens from the Smithsonian’s collection.

Earth OLogy amnh.org/explore/ology/earthHands-on activities and articles for kids 7 and up, including: • Grow Rock Candy: use sugar to make and compare crystals• Jade: find out why a mineralogist thinks jade is so special • If Rocks Could Talk: meet six rocks from Mexico, Scotland, and even outer space!

Microminerals amnh.org/belskymicromineralsAn annotated, interactive guide to the Hall’s Howard Lee Belsky Memorial Exhibit of Microminerals (microscopic-sized mineral crystals).

Profile: George Harlowamnh.org/explore/amnh.tv/(watch)/meet-the-scientists/profile-george-harlowA video portrait of crystal chemist, jade specialist, and Museum curator George Harlow.

Gold amnh.org/exhibitions/past-exhibitions/goldExplore a variety of topics related to this soft and lustrous metal, prized across history and around the world. Includes links to this exhibition’s Educator’s Guide and other resources.

Zircons: Time Capsules from the Early Earth amnh.org/explore/science-bulletins/zirconsTravel to Greenland and a zircon-making lab in New York State to learn why these intriguing mineral crystals are the basis of new hypotheses about Earth’s first 500 million years. Nine-minute video.

Gem pocket

Sapphires

Star of India

Quartz

Atoms, space lattices, and crystals

Physical properties of minerals

Chemical properties of minerals

Optical properties of minerals

Metamorphic environment

Magmatic environment

Pegmatite environment

Hydrothermal environment

Hydrothermal and metamorphic environment

Evaporite environment

Volcanic environment

Sedimentary environment

© 2013 American Museum of Natural History. All rights reserved.

of the HallsMAP

GUGGENHEIM HALL OF MINERALS

Properties of Minerals Mineral Forming Environments

MORGAN HALL OF GEMS

1a

1b

1c

1d

1a

2a2h

2g

2f

2e 2d

2c

2b

1b

1d

1c

2a

2b

2c

2d

2e

2f

2g

2h

3a

3b

3c

3d

3a

3b3c

3d

CALIFORNIA GOLd

COMMONMINERALS

NATURE OFMINERALS

MICROMINERALS

INTRO TOMINERALOGY

ESTHETICMINERALS

SYSTEMATIC MINERALOGY

PROPERTIES OFMINERALS

ENERGYANd

MINERALS FOREVERGOLdVIdEO

MINERALFORMING

ENVIRONMENTS

3d. Quartz: Some min-erals, like garnets and diamonds, have the same name as their gemstones. In other cases, the same mineral can give rise to different gemstones because its color varies. So purple quartz is called amethyst, and yellow quartz is called citrine. Have students observe the way different quartz specimens vary in color and clarity, and compare uncut (natural) specimens to cut ones.

Have students locate the February and November birthstones in this case. Then, invite them to find the others around the hall and to note which minerals (in parentheses) give rise to multiple gems.

GUIdEd EXPLORATIONS

Tip: Bring small flashlights so students can see how specimens react to beams of light.

3a. Gem pocket: Minerals are the building blocks of rocks, and form as rocks form. Mineral crystals are typically small, but sometimes grow to large sizes. This is a recreation of a natural, crystal-filled cavity that was found in the mountains of California. Have students find all seven examples of large mineral crystals: tourmaline, albite, quartz, kunzite, morganite, lepidolite, microcline.

3b. Sapphires: A few minerals are used as gems in their natural crystal form. Most, however, are shaped and polished to bring out their sparkle, brilliant color, and/or unusual texture. Gems that are transparent, like

these sapphires, are normally faceted: cut with a machine that polishes small, flat windows (called facets) at regular intervals

and exact angles. This maximizes light reflected by the stone, highlighting its optical properties and causing it to sparkle. Invite students to observe the visual effects of different types and numbers of facets.

3c. Star of India: Stones that are not completely transparent are usually shaped and polished into cabochons: a smooth dome shape. This shows off the stone’s color or surface properties, as with opals and star sapphires like this famous 563-carat stone. The ball-like Star of India has stars on both sides. This pattern is caused by tiny fibers of the mineral rutile, which reflect incoming light in a three-dimensional pattern called asterism and also give the gem its milky quality.

An array of precious and ornamental stones — some uncut, polished, or in elaborate settings — is on exhibit in this hall. Drawn from the Museum’s collection of more than 100,000 minerals and gems, specimens are organized by mineral group and include precious metals. Several cases feature decorative objects and jewelry, which span three millennia and many cultures.

What Makes a Gem?

© 2013 American Museum of Natural History. All rights reserved.

Teaching in the HALLMORGAN MEMORIAL HALL OF GEMS

Gemologists use certain properties, some listed below, to determine the quality of a gem.

Color: depth (not too dark or pale), uniformity, fluorescence Clarity: transparent, translucent, opaque Hardness: resists scratching (7+ on Mohs scale)Durability: will not shatter, crack, or cleaveBrilliance: high index of refraction, high lusterSpecial optics: iridescence (play of colors), cat’s eye or star effects

did you know? Carat karat. (Or carrot.)Carat is the standard unit of weight (mass) for gems — not to be confused with karat, the unit of measure-ment of gold purity. However, both are based on the carob seed, an ancient measure of weight.

January: garnet (garnet)February: amethyst (quartz)March: aquamarine (beryl)April: diamond (diamond)May: emerald (beryl)June: moonstone (feldspar)July: ruby (corundum)

August: peridot (olivine)September: sapphire (corundum)October: tourmaline (tourmaline)November: citrine (quartz)December: topaz (topaz)