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Let's Collect Rocks & Shells
Let's Collect Rocks & Shells
CONTENTS
COLLECTING SEASHELLS
SEASHELLS. . .WHAT ARE THEY?
THE SHELL AS AN ARCHITECT
LET'S MEET SOME SHELLS
WHERE TO LOOK
STARTING A COLLECTION. . .HERE'S HOW
COLLECTING ROCKS
ROCKS ARE MADE OF MINERALS
MAIN KINDS OF ROCKS
COLLECTING
GEMS FOR THE LUCKY FEW
INTRODUCTION
Millions of people throughout the world have found many hours
of pleasure, adventure and education by collecting either rocks
or shells.
This booklet won't tell you everything there is to know about
rocks and shells. That would require many large volumes. We only
want to arouse your curiosity about two delightful pastimes that
are so broad and varied that they can lead to a career or a
satisfying hobby.
Shell Oil Company's interest in the subjects comes from its
history and the nature of its business. The name--chosen by a
company that was founded years before anyone thought of drilling
for oil--comes from the seashells this company brought from the
Orient for use in mother-of-pearl items such as buttons and knife
handles.
Now its world-famous emblem (the Pecten) is recognized by millions
of people in every walk of life. It's on service stations, trucks,
buildings, oil derricks and chemical plants. Even the company's
industrial lubricants are named for shells because shells have
the same scientific names everywhere in the world.
For an oil company, rocks have a special interest. Crude oil is
found not in underground lakes or pools but in the tiny spaces
between grains of sand or in the pores of rocks. Only certain
types of rock formations are favorable to the accumulation of oil.
Thus, oilmen need to know everything they can about the right kind
of rocks.
Shell has scientists who work with rocks all day and laboratories
filled with rock, mineral and crystal specimens. We are always
learning new things about them.
The pages that follow provide basic information about two subjects
that can be richly rewarding whether you follow them for profit,
as Shell does, or for pleasure, as millions of people around the
world do.
SEASHELLS. . .WHAT ARE THEY?
First, a seashell is one of the 100,000 species of backboneless
animals belonging to the zoological group known as the Mollusca.
Mollusks include not only the familiar clams, scallops and snails,
but also the squids, octopus and Chambered Nautilus. Other "shells"
found in the ocean include those of crabs, lobsters, barnacles and
sea urchins.
True molluscan shells come in two main varieties: BIVALVES and
UNIVALVES. Bivalves have two valves, fitting together along a
toothed hinge on one side, and kept closed by means of ADDUCTOR
MUSCLES. Univalves have only one shell, usually coiled, but
sometimes shaped like a cap or miniature volcano. Some marine
univalves can seal themselves inside with an operculum, which
covers the open end of the shell like a trap door. Although shells
take on many different shapes, they are much alike inside. Each
has a foot, a breathing siphon, a tiny brain and heart, and a
fleshy mantle which secretes lime for shell-building. Most true
mollusks have eyes, but a few are blind. Many have teeth, called
RADULAE.
Like any other animal, the mollusk generally moves about. It
pushes along on the ocean floor on its foot, or it might swim a
little. It lays millions of eggs and hatches countless baby
mollusks. It lives its life in its shell, lugging it around,
snuggling into it when alarmed, burrowing into mud, fastening
itself to a rock and creating ingenious camouflage. It builds its
calcareous house with a great instinctive talent for color and
sculpture. . .and the closer it lives to the tropical zones, the
more beautifully spectacular is its art.
The two parts of a bivalve shell are like thin saucers, concave
inside, convex outside. The inside is smooth, polished. The outside
is rougher, sometimes with graceful ribs or concentric ridges or
combinations of both. Univalves are conical and spiraling, with
a series of whorls coming down like widening steps from the tiny
nucleus on top. Univalves may have spines on their shoulders.
The opening, called the aperture, has a delicate right-hand rim
called the lip and a heavy, left-hand edge called the columella.
[figure captions]
BIVALVE'S anatomy: a) foot, b) adductor muscles, c) gills, d) hinge,
e) adductor muscles, f) siphon, g) stomach, h) mantle. Oysters,
clams, mussels all have them.
UNIVALVE'S anatomy: As before, a) foot, b) siphon, c) mantle, but
also d) operculum. Univalves include whelks, winkles, conchs.
Chambered nautilus is brother to the octopus, but he wears his
castle permanently--and on the outside.
THE SHELL AS AN ARCHITECT. . .HOW DOES HE DO IT?
Picture a vast undersea factory with billions of shells in constant
production. Each is made slowly and entirely of lime which the
little animal inside extracts from its food, almost from the first
day of its life. Each shell builder flawlessly follows the shape
and design of the species to which it belongs.
All these sea animals come from eggs, all different according to
species, but all laid in measureless abundance--sometimes released
into the open sea, sometimes protected in homemade nests, sometimes
encased in capsules strung like beads. Hatched, most baby mollusks
swim freely for a while, their tiny, transparent bodies almost
invisible to the naked eye. Then they start building a heavier
shell and sink to the bottom.
Each shell's mantle contains a network of microscopic tubes. Each
tube secretes a tiny amount of lime which instantly adheres to the
shell. The animal builds his shell to the proper size and thickness
and determines its ridges and whorls. Some kinds of shells take
two to five years to reach maturity. Others keep growing all their
lives. Color tubes are spaced like holes on a player piano roll
allowing pigments to tint the shell at the right spots in the growing
design. Many shells are covered with a self-made brown sheath, the
PERIOSTRACUM.
[figure captions]
Most shells don't change basic structure as they grow. Young
COWRIES (l.), however, alter greatly in maturity (r.).
Tough, lozenge-shaped egg cases on this string hatch baby WHELKS
like ones shown.
Newborn mollusks are usually free swimming, moved by hairs. Shell
is there, but transparent for a few days.
LET'S MEET SOME SHELLS
Latin abounds in conchology, as you've already noticed. Why?
Well, because this is a hobby and science that spans the world.
Englishmen, Frenchmen, Greeks and Indians all have their own local
names for shells. But scientists everywhere give things in nature
Latin names. Shells of the same sort carry the same Latin label
on every beach in every sea. Much of the fascination of shell
collecting is learning these names and how they were derived. . .
for shells have been named for almost everything. We can't catalog
100,000 species here, but let's call off the names of a few of the
interesting specimens you might come across.
Many shells have wonderfully descriptive names. For example, there's
ARCA ZEBRA, which has stripes and looks like a miniature turkey wing
and is commonly called Turkey Wing. Then there's a scallop called
the Lion's Paw; NERITA PELORONTA, or Bleeding Tooth; and CYPRAEA
CERVINETTA, "little deer cowrie" which resembles a spotted fawn.
(Cowrie is a common name for a kind of shell used as money in parts
of Africa and Asia.)
There are shells named for people: CONUS JULIAE ("Julia's cone
shell"), PLEUROTOMELLA JEFFREYSII ("Jeffrey's Pleurotomella"),
and ACLIS WALLERI ("Waller's Aclis"). Many are named for the place
they were first discovered: UROSALPINX TAMPAENSIS, Tampa Drill;
and IPHIGENIA BRASILIANA, Brazil Clam.
Some shells take their names from flowers: FASCIOLARIA TULIPA,
Tulip Shell. Many get named from mammals--not always too
accurately. CYPRAEA TIGRIS and CYPRAEA ZEBRA both have spots, not
stripes. But CYPRAEA TALPA ("mole cowrie") does look a lot like a
mole. Then there's (let's skip the Latin this time) Magpie Shell,
Mottled Dove Shell, Mouse Cone, Horse Conch, Checkered Pheasant,
and Cuban Frog Shell. There's mythology: Venus, Neptunea, Pandora,
Tritonis. Music: Buccinum ("trumpet"), Citharas ("guitar"), Harpa.
Religion is represented, too. In the genus MITRA are species
PONTIFICALIS, EPISCOPALIS, PAPALIS, and PATRIARCHALIS. Some other
fanciful names are: Great Heart, Jewel, Box, Rising Sun, Checkerboard,
Wood Louse, Writhing Shell, Sundial, Key-Hole Limpet, Red Turban,
and Black Lace Murex. And that's where we stop and draw breath.
You'll find others--there are literally thousands more!
You've got to be a detective. These little animals are the natural
food for many of the larger undersea creatures, so one of their
greatest talents is hiding. Approaching danger, whether from
octopus, fish or man, arouses caution in a small mollusk and it
becomes as inconspicuous as it can. This can be pretty inconspicuous,
as the novice conchologist learns early in his search.
REMEMBER - by all means, don't be a landlubber. Get into the water.
No matter whether you go shelling up North, down South, in the West
or in the Tropics, you won't get any satisfaction (or value) from
collecting dead shells washed up on a beach. To build a good
collection, you should take your mollusks alive, then clean and
prepare them yourself. (More about that later.) You won't find
live ones unless you go where they live.
[figure captions]
CONUS SPURIUS
"ALPHABET CONE"
CYRTOPLEURA COSTATA
"ANGEL WING"
TEREBRADISLOCATA
"ATLANTIC AUGER"
MUREX DILECTUS
"LACE MUREX"
EPITONIUM HUMPHREYSI
"HUMPHREY'S WENTLETRAP"
LYROPECTEN NODOSUS
"LION'S PAW"
FASCIOLARIA DISTANS
"BANDED TULIP"
DIODORA CAYENENSIS
"KEYHOLE LIMPET"
ANATINA PLICATELLA
"CHANNELED DUCK"
WHERE TO LOOK*
Many shells are endowed with perfect camouflage. The colorful
seafans off Florida are hiding places for the SIMNIA whose long
purple or yellow shells, clinging to sea fans and matching
perfectly in color, are nearly indiscernible. Other shells create
disguises as they go along. In Florida waters, a pile of dead and
broken shells may be worth investigation: XENOPHORA CONCHYLIOPHORA
("carrier shell") might be under it; it cements the old, discarded
shells to its own. Northern tide pools accommodate many kinds of
LITTORINA ("periwinkles"). These pretty little shells, in shades
from yellow to brown, are well concealed among the dimly-lit seaweed.
Along any rocky shore, limpets grow as wide as two inches but
remain hard to find. Their turtleback shells, covered with moss,
look just like rocks, and they stick so tightly to the big stones
that--even when they are seen--they can scarcely be pried loose.
Abundant on wave-washed beaches of both the North and the South
are dead shells of another perfectly camouflaged clam called
ARCA. While alive, the shells are covered with hairy, brown or
black epidermis and look like pebbles among tufts of seaweed and
marine grass.
On the West Coast, the abalone is a most typical species in
addition to being a delicious food. The bright-hued shell is widely
used for souvenirs such as ash trays and is in demand for buttons
and decorative purposes.
Most shells of interest to the collector are found in the sea--
but not all. Living forest mollusks have been found 18,000 feet
high in the Himalayas. And in this country a great variety of
mollusks live in rivers, ponds, and even hot springs. Several
species are peculiar to the Nile River. Also, species of mollusks
live on land--for example the common garden snail.
Wherever you go, be it the South Seas, a mountain lake, or the
shoals off the Gulf Coast, you'll find shells to collect and
opportunities to expand your hobby.
*Collectors should familiarize themselves with local regulations.
In some areas, such as parks and marine sanctuaries, collection
of shells and other marine organisms may be restricted or prohibited.
STARTING A COLLECTION. . .HERE'S HOW
Knowing WHERE to look for shells you probably wonder WHEN is the
best time. The answer is ANYTIME. Mollusks know no season. Some
species appear suddenly for several days and then vanish; others
can be found almost anytime. Most mollusks appear at night, but
others work only in the daytime and go out of sight after dark.
The tides may have something to do with it. So does the weather--
it can be hot or cold, dry or rainy. While you won't find the same
shell at all times, you'll find a great variety at any time.
What to take? The things pictured on page 8 should be enough.
If you're going out on the coral reefs along Florida, it would be
wise to keep your legs covered as protection against stings or
scratches. Don't ever forget to wear some kind of shoes in the
water. Even though you're wearing a mask or goggles, take along
a gig or some slender stick and feel your way along so you don't
fall into a hole you can't see in the deceptive near-tropical
waters. If, despite precautions, you get a sea urchin's needlelike
spine broken off in your skin, soak the wound in vinegar which will
dissolve the fragments and stop the pain in a few minutes.
Tiny shells buried in sand can be netted in your sieve. Clinging
ones must be chiseled off rocks. Frail, delicate clingers should
be gently nudged loose with tweezers. Submerged sandbars are good
spots to find several kinds of univalves and bivalves, but the
latter will dig themselves quickly out of sight--as far down as
several feet. When you see one going underground, don't dig directly
over it--you might break its shell. Instead, dig to one side, and
break the mud or sand away with your hands.
After you've had a good day's haul and a rest (you'll need one)
you must clean your shells. Put your tiniest, most fragile ones
in rubbing alcohol. Put the rest in a pot of fresh water and slowly
bring it to a boil. Let them cool in the water slowly to prevent
the glossy shells from cracking. When cool, your bivalves will be
gaping open; simply scrape them clean. Your univalves will be
more difficult; remove the animal with a crocket hook or other
piece of bent wire, turning it gently with the spiral; try to get
it out whole to save yourself trouble. Save the univalve's operculum
and slice it off the muscle that holds it. It will preserve
indefinitely and is a valuable part of the shell.
Clean the shell's exterior by scraping it gently with a dull knife
or nail file, then soaking it in a Clorox solution (1 cup to 2
quarts water) for two hours. Some will be covered with an ugly
skin--scientists keep this intact and you should try to. The best
collection has two of each species--one with and one without the
epidermis.
After your clean shells have dried (in shade, not sun), go over
them with a rag dampened in light oil. This insures preservation
and restores their natural luster. Every three months or so, rub
them with oil again--their most delicate colors will remain
brilliant for years. Don't ever use shellac, lacquer or varnish.
Get a reference book from your library and identify your shells.
Keep an account of when and where you collected them.
Store your shells in closed containers to protect them from
sunlight and dust. Almost any set of small drawers or a cabinet
will do. Matchboxes or pillboxes are excellent for small specimens.
For display purposes, glass-covered cases are best to prevent
handling of the shells. A shell's beauty is often deceptive. Many
unattractive and drab shells are worth hundreds of dollars while
the most colorful are frequently valued at a dollar or less. The
rarity of a species determines its value. A truly valuable shell
may come from deep, inaccessible waters or remote lands--or it may
be one of an extinct species. A Slit Shell collected 100 fathoms
down in waters off the British West Indies is valued at $1000.
Another undersea treasure, the Glory-Of-The-Seas, was first found
in 1771 and one time would bring the conchologist $1500. The
greatest rarities, however, are truly valueless and are not for
sale.
. . .And there it is, the fascinating hobby of shell collecting.
It's a lot of work--but a lot of fun, too.
[figure captions]
Take a SIEVE. Or an orange sack. Besides carrying your shells,
it may help you catch them. A few pint BOTTLES will hold delicate
ones.
MASK (or goggles) is essential for looking underwater. Bathing
suit or old clothes, of course. High shoes (or sneakers)--never
go barefooted! Heavy cloth GLOVES. Watch out for sunburn!
GIG or fish spear (if you're going South) to keep pesky crabs,
sea urchins off. CLAM DIGGING HOE or trowel for burrowing shells.
VINEGAR for first aid, in case you're stuck by urchin's spines.
CHISEL and HAMMER to get the clingers, spatula for frail limpets.
You may find other hardware handy, but these are basic.
NOW LET'S LOOK AT ROCKS
ROCKS ARE MADE OF MINERALS
Rocks, to begin with, are made of minerals. What is a mineral?
The definition may sound difficult--a mineral is a chemical element
or compound (combination of elements) occurring naturally as the
result of inorganic processes. But don't be discouraged. Things
will clear up soon.
The world contains more than 1,100 kinds of minerals. These can
be grouped in three general classes.
1. METALLIC MINERALS. These include things most of us would think
of if we were asked to name some minerals. Familiar examples are
copper, silver, mercury, iron, nickel and cobalt. Most of them are
found in combination with other things--as ores. We get lead from
galena, or lead sulfide. Tin comes from the ore cassiterite; zinc
from sphalerite and zincblende, or blackjack. Chromium that makes
the family car flashy comes from chromite. Many minerals yield
aluminum. Uranium occurs in about 50 minerals, nearly all rare.
Twenty-four carat gold is a metallic mineral. A 14 carat gold ring
contains 14/24 or 58% gold.
An average sample of earth contains 9% aluminum, 5.5% iron, .01% zinc,
.008% copper, .004% tin, .002% lead, .0005% uranium, and .0000006% gold
or platinum. It would be hopelessly expensive to recover such metals
from an average ton of earth. That's why metallic minerals are taken
from concentrated deposits in mines.
Many valuable minerals are found in veins running through rock. Veins
can be formed when: (a) mineral-laden ground water seeps into cracks,
evaporates, and leaves mineral grains that build up into a vein;
(b) hot water from deep within the earth fills cracks, then cools
and deposits much of the material in solution as minerals in a
vein--sometimes including metals such as gold and silver; (c) molten
gaseous material squeezes into cracks near the earth's surface,
then slowly hardens into a vein.
2. NONMETALLIC MINERALS. These are of great importance to certain
industries. You will find them in insulation and filters. They are
used extensively in the ceramic and chemical industries. They include
sulfur, graphite (the "lead" in pencils), gypsum, halite (rock salt),
borax, talc, asbestos and quartz. Undoubtedly, you'll have some
nonmetallic minerals in your collection. Rocks containing asbestos
are especially handsome and varied.
3. ROCK-FORMING MINERALS. These are the building materials of the
earth. They make mountains and valleys. They furnish the ingredients
of soil and the salt of the sea. They are largely silicates--that is,
they contain silicon and oxygen. (Silicon is a nonmetallic element,
always found in combination with something else. It is second only
to oxygen as the chief elementary constituent of the earth's crust.)
Other rock-forming minerals are the large family of micas, with names
like muscovite and phlogopite. There are the feldspars, including
albite and orthoclase. Others are amphiboles, pyroxenes, zeolites,
garnets and many others you may never find or hear about unless
you become a true mineralogist.
A rock may be made almost entirely of one mineral or of more than
one mineral. Rocks containing different combinations of the same
minerals are different. Even two things made of the same single
mineral can be quite different. Carbon may turn up as a lump of
coal or a diamond.
How Minerals Got Their Names
Names of most minerals end in "ite"--apatite, calcite, dolomite,
fluorite. But many do not: amphibole, copper (the most common pure
metal in rocks), feldspar, galena, gypsum, hornblende, mica, quartz.
Many minerals take their names from a Greek word referring to some
outstanding property of the mineral. For example, hematite,
an oxide of iron, was named about 325 B.C. from the Greek HAIMA,
or blood, because of the color of its powder.
Some minerals are named for the locality in which they were first
discovered. Coloradoite was first found in Colorado. Benitoite
turned up in San Benito County, California. And so with labradorite
and brazilite.
Other minerals got their names from famous people. Willemite was
named in honor of Willem I, King of the Netherlands. The great
German poet-philosopher, Goethe, could turn up in your collection
as goethite. And there's smithsonite, named for James Smithson,
founder of the Smithsonian Institution.
[figure captions]
Gold, jasper, uncut diamond, quartz (violet in color), halite
(Carlsbad N.M.), calcite (S. Dakota), copper, turquoise (brilliant
color)
Out Of This World
Some minerals come from outer space. They're meteorites, which
are rock fragments. Every day, hundreds of millions of them
enter the earth's atmosphere. Most of them, however, are burned up
by the heat from air friction and never reach the ground. Meteors
large enough to reach the earth are called meteorites. Most minerals
found in meteorites are the same as those we have on earth. But,
there are some rare minerals known only in meteorites. Two of them
are cohenite and schreibersite.
MAIN KINDS OF ROCKS
Rocks are the building blocks of the earth's crust. They may be
massive, as in granite ledges, or tiny. Soil, gravel, sand and clay
are rocks. THERE ARE THREE MAIN TYPES OF ROCKS.
1. IGNEOUS rocks are those formed at very high temperatures or from
molten materials. They come from magmas--molten mixtures of minerals,
often containing gases. They come from deep below the surface of the
earth. If they cool off while below the surface, they form intrusive
rocks, which may later be revealed by erosion. When magmas reach the
surface red hot, they form extrusive rocks, such as volcanic rocks.
Thus, granite is an igneous, intrusive rock; lava is an igneous,
extrusive rock. (Notice how the type of rock tells its past
history--if you know what to look for.)
2. SEDIMENTARY rocks are formed by the action of wind, water, or
organisms. They cover about three quarters of the Earth's surface.
Most are laid down--as sediments--on the bottom of rivers, lakes
and seas. Many have been moved by water, wind, waves, currents,
ice or gravity. The most common sedimentary rocks are sandstones,
limestones, conglomerates and shales. Oil is found in sedimentary
formations.
3. METAMORPHIC rocks are those that have been changed from what
they were at first into something else--by heat, pressure, or
chemical action. All kinds of rocks can be changed. The result
is a new crystalline structure, the formation of new minerals,
or a change in the rock's texture. Slate was once shale. Marble
came from limestone. Gneiss (pronounced "nice") is perhaps
reworked granite.
[figure captions]
Igneous rocks are formed at high temperatures or from molten
materials. They come from deep beneath the earth. They can be
intrusive or extrusive--depending on where they cooled off.
Sedimentary rocks are formed by the action of wind, water, or
organisms. They usually are laid down on the bottom of rivers,
lakes and seas. Most of the earth's surface is covered by these
rocks. Oil is found in sedimentary formations.
Metamorphic rocks have been changed from their original state
into something else. Heat, pressure, chemical action change the
crystalline structure, the texture, even form new minerals. All
kinds of rock can be changed.
A Word On Fossils
Perhaps you'll find rocks containing fossils--or even fossils
by themselves. They should form a separate part of your collection.
Fossils are the remains--or the outlines--of former plant or
animal life buried in rock. The older the rock, the simpler the
plant and animal life it contains. Thus fossils can give a clue
to the age of the rock strata.
Fossils can teach history. They tell us about plants and animals
that are now extinct--the dinosaur, for example. They can also tell
of ancient climates. Coral found in rocks in Greenland suggests it
must have once been warm. Remains of fir and spruce trees have been
found in the tropics.
How are fossils formed? Teeth, bone and wood don't last long in
their original state. However, buried materials decompose, leaving
a film of carbon as a fossil. This results in a leaf tracery, or
the outlines of some simple animal. On a gigantic scale, this process
of forming carbon has resulted in our great coal deposits.
Sometimes the buried material is gradually replaced by silica or other
substances, making petrified objects. Wood can be replaced--cell by
cell--by agate or opal from silica-bearing water. The result is
petrified wood, the finest examples of which can be found in our
Petrified Forest National Park in Arizona. This can happen to
shells, too.
How about molds and casts of footprints of ancient animals? A
brontosaurus might have stomped along in soft, warm mud eons ago.
The mud hardened and later another layer of soft earth covered the
print, preserving it.
COLLECTING
If you want to collect rocks and minerals just for the sake of
having them, you can buy specimens. Many can be purchased for
25 cents to $1 each, while a rare specimen can cost hundreds of
dollars.
The true pleasure is in finding your own samples. Later, when you
have a good-sized collection, you can fill gaps by buying specimens
or swapping extras with other collectors. You'll be amazed at the
number of amateur collectors. Perhaps no branch of science owes more
to the work of amateurs than mineralogy. Our great collection of
minerals in the U.S. National Museum in Washington, D.C., was
gathered almost entirely by two amateurs who devoted many years
and much money to their hobby.
Where To Look
Look for pebbles by the roadside, in beds of streams and riverbanks.
Go out into the country for ledges on hillsides. Every road cut,
cliff, bank, excavation, or quarry shows rocks and minerals.
Railroad cuts, rock pits, dump piles around mines, building
sites--they'll all yield specimens. Some of the best mineral
specimens collected in New York City came from skyscraper and subway
excavations. Help a New England farmer clear his field and you'll
have more rocks than you know what to do with.
As for reference books, many states publish guides to mineral
deposits. Mineralogical magazines list mineral localities.
Tips For The Field
Don't try to collect too much at once. Work early in the day or
late in the afternoon. A hot sun on bare rock can make you
sizzle--especially if you're loaded with equipment and samples.
Here's the equipment to take: newspapers for wrapping samples,
notebook and pencil, geologist's pick, cold chisel, magnifying
glass, compass, heavy gloves, a knife, and a knapsack. Later on,
you may want a Geiger counter for spotting radioactive rocks.
Be selective. Hand-sized specimens are best. If your sample is
too large, trim it to size, showing its most striking feature
to best advantage. When you wrap the sample in newspaper, include
a note telling when and where you found it. This information will
be transcribed to a filing card when you add the specimens to your
display, so make it as complete and accurate as you can.
When you get home, clean specimens with soapy, warm water, applied
with a soft brush. Soluble minerals like halite can't be washed,
but should be rinsed with alcohol. A coat of clear lacquer will
protect some samples against dirt.
Arranging Your Collection
Put a spot of enamel on the specimen. Write on the spot--in India
ink--a catalog number and have this number refer to a card in a
file drawer. The card should list date, place found, identification
of specimen, etc.
Group your samples: metallic minerals, semiprecious stones, nonmetallic
minerals. Display them on a shelf, or buy or build a mineral cabinet
with partitioned drawers. For smaller samples, use a Riker mount
with a glass top.
[figure captions]
A common rock
Here's the equipment to take: newspapers for wrapping samples,
notebook and pencil, geologist's pick, cold chisel, magnifying
glass, compass, heavy gloves, a knife, and a knapsack.
What Do I Have?
How do you identify specimens?
Get books and magazines on rocks and minerals. Many have colored
pictures that help.
But identification is best made by noting the physical characteristics
of the rock or mineral. For minerals, there's a hardness scale in
which a mineral of the higher number can scratch a mineral of the
lower number but not be scratched by it. The scale is: 1) talc;
2)gypsum; 3) calcite; 4) fluorite; 5) apatite; 6) orthoclase;
7) quartz; 8) topaz; 9) corundum; 10) diamond. Remember it by
this silly sentence: "The girls can flirt and other queer things
can do."
When on a trip, remember that a fingernail has a hardness of 2.5;
a penny, 3; a knife blade, 5.5; and a steel file, 6.5. Use these
to scratch your sample and you can get an approximate idea of its
hardness.
You can buy a set of hardness points. They're pointed pieces of
minerals set in brass tubes, each marked with its hardness scale.
The set costs about $30 (half that if you assemble your own).
Other tests for identifying minerals include specific gravity
(weight of mineral compared to the weight of an equal volume of
water), optical properties and crystal form, color and luster.
Minerals differ in cleavage and fracture (how they come apart
when cut). They leave distinctive streaks on unglazed porcelain.
Some are magnetic, some have electrical properties, some glow under
ultraviolet or black light, some are radioactive, some fuse under
a low flame while others are unaffected. Many studies with the
dissolved mineral can identify it beyond doubt.
But most of these are too complicated for the beginner. As you read,
look at pictures and samples, and talk with other rockhounds or
leaders of mineralogy clubs, you'll get better at identifying rocks.
Museum experts and your state's geologist can help, too.
[figure captions]
Specific gravity balance
Blowpipe analysis
GEMS FOR THE LUCKY FEW
If you're lucky, you'll find gems or semiprecious stones. Gems are
the finer, more crystalline forms of minerals which are ordinarily
less beautiful and spectacular. The true gems are diamonds, emeralds,
rubies and sapphires. All others are semiprecious and ornamental.
Diamonds are pure carbon, but did you know that rubies and sapphires
are corundum minerals--rare forms of alumina. In slightly different
form, they'd turn up on emery paper.
Other stones you might find are the quartz gems: rose quartz,
amethyst, rock crystal, agate, jasper, bloodstone. Or opaque gems
such as jade, moonstone, lapis-lazuli, obsidian, and turquoise.
You don't have to find them. You can buy gems in the rough or in
blanks, then cut and polish them to make your own jewelry or
decorations. This takes practice, plus a cutting and polishing
outfit, wood vise, maybe a diamond wheel. (Or you can join a
lapidary club that might already have the equipment).
First learn to make cabochons--stones with round or curved surfaces.
Then try cutting facets (or faces) in transparent gems. Learn by
reading, working with an expert, trial and error. Making jewelry
is fun, and collecting gems is as interesting as collecting rocks
and minerals; it brings the world into your home. From the West
come agates, jaspers, petrified woods; from the East, colorful
marbles, serpentines, granites. Alaska, Idaho, Connecticut or
Austria will yield dark red garnets. Fine moonstones come from
Ontario; quartz crystals from Hot Springs, Arkansas, can be compared
with similar ones from the Swiss Alps or Brazil.
Rock collecting is a hobby you can tailor to your taste. But
whether you concentrate on an area close to home or travel across
whole continents, you'll find that the pleasure and knowledge you
gain from your collection are matched by the fun and adventure of
the search.
[figure captions]
Drop sticks to hold stones
Diamond cutting wheel
[BACK COVER]
A Brontosaurus
Shell Oil Company
Revised 8/88
