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Identify that Rock Updated 12-01-09 Copyright 2008 Shelby Raymond, Skeena Storm Stones Page: 2

(clockwise from top center): (1)gabbro, (2)diorite,(3)scoria, (4)basalt, (5)pumice, (6)granite, (7)tuff, (8)

obsidian

STEP 1: ROCK TALK

Well start with a couple of definitions so thatwe are all talking the same language!

I g n e o u sIgneous rocks are formed when meltedrock, from deep inside the earth or avolcano, makes it way to the surfaceand then cools quickly. e.g. granite

and obsidian

2 T y p e s o f I g n e o u s Ro c k s :

a. Intrusive = magma that coolsbeneath the surface (i.e. granite)

b. Extrusive = magma that coolsabove the surface, i.e. lava, basalt

(clockwise from top, center) (9)oil shale, (10)breccia,

(11)shale, (12)conglomerate, (13)limestone, (14)arkose,(15)lignite coal, (16)fossiliferous limestone, (17)

brachiopod limestone,(18) travertine, (19)sandstone,(20)calcareous tufa

Se d i m e n t a r ySedimentary rocks are formed whenstuff piles up like stones, shells,plant material, etc. As these itemspile up on top of one another, they putpressure on the bottom layer, whichcauses the items to stick together eventually forming a solid rock. Quitefrequently youll be able to see thelayering effect.

Sedimentary rocks can be used inmaking jewelry, however, most arevery soft and need to be stabilized orplaced in epoxy to protect them fromevery day bumps and even weather!

You will find fossil evidence insedimentary rocks more frequentlythan the other two types. This isbecause the heat involved in thecreation of igneous stones usuallydestroys the object. Heat and pressurefrequently destroy potential fossilobjects during the creation ofmetamorphic stones.

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6

5

2

3

4

1

8

9

10

11

19

1820

1316

14

17

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3 Main Categories of Rock:1. Igneous2. Sedimentary3. Metamorphic


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Amethyst is a type of Quartz (both pictured above) and is

considered a semi-precious stone.

To the left is a fluorite crystal; fluorite

crystals are octahedral (they have 8sides). Most minerals have a typical

crystal formation and this can help you

identify stones.

C r y s t a l :A crystal is the form a mineral takeson as it grows. You have probablyseen crystals such as rose quartz oramethyst. The biggest crystals areusually found in areas where there isroom to grow crevices and caves. Do

a search on the internet for the giantselenite gypsum crystals found in theNaica mine, Cave of Swords, south ofChihuahua City, Mexico you WILL beamazed!

Gem:Its kind of challenging to define whata gem is. Usually gems are the hardeststones, such as diamonds and ruby -although opals give lie to thatdefinition! Gems are also usuallyformed in igneous or metamorphicrock. They are also usually quite rare in fact, the rarer the stone, the morevaluable it tends to be. Gems areusually brighter and contain fewerimpurities than their semi-preciouscousins.

M i n e r a l : Minerals are the building blocks of theuniverse. Most rocks are made up ofminerals. Each mineral has a clearly,

scientifically defined chemical contentand the atoms are put together,arranged, in a very specific way.

MOHS Scale of Hardness1. Talc2. Gypsum3. Calcite4. Flourite5. Apatite (turquoise, lapis lazuli)6. Orthoclase feldspar (epidote,

labradorite)7. Quartz (amethyst, aventurine)8. Topaz (spinel, zirconia)9. Corundum (ruby, sapphire)10.Diamond

Quickie MOHS2.5 = fingernail 5.5 = pocket knife3.5 = penny 6.5 = steel file

MOHS Scale of Hardness

The MOHS Scale of Hardness is a quick andeasy guide to help you figure out how hard arock is and it also aids you in identifying therock. The softest stone is Talc at number 1,with diamond being the hardest at number10.

Harder minerals (higher numbers on thescale) will scratch softer ones (the ones withsmaller numbers). i.e. quartz will scratchorthoclase, apatite, fluorite, calcite, gypsumand talc, but it will notscratch topaz,corundum or diamond!

Grossular garnet, var. Hessonite inmetamorphosed impure limestone matrix

garnet (gem)


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This is a great bookthat was written by alocal geologist. Withthis knowledge inhand, combined withinformation on what

formations are likelyto contain specificstones, my rock huntsare usuallysuccessful.

Map of world showing the distribution of major deposits plotted on digital

elevation model with draped geology from Geological Survey of Canada,Open File 2915d, 1995.Data from thesynthesis of ore deposits. Data

plotted and diagrams prepared by W.D. Goodfellow.

The Skeen River, Terrace, British Columbia, Canada

STEP 2: KNOW YOUR PLACE

Learn about the area in which you live, orplaces you can easily visit. Usually itspossible to find a rockhound group,lapidary or mineral society. They are

wonderful sources of information.

Government websites also haveinformation on the geography andgeology of most regions. Its easy todownload maps or brochures that detailwhat kinds of minerals and rocks may benearby.

Take a class in geography, geology orrockhounding. Not only will you meetpeople with similar interests, but you mayalso learn of some new collecting sites!

STEP 3: MIND YOUR MANNERS

Whenever you are out looking for rocks,have a rockhounding buddy with you andmake sure others know where you aregoing and approximately when you willreturn.

Always get permission before enteringprivate land. When in doubt, check withlocal authorities.

Be careful. Take a first aid kit and knowthe local numbers for emergencyassistance. Avoid active slide areas nomatter how great the find! Rememberthat caves can be dangerous only enterwith a trained spelunker.

Know the type of rocks and minerals youwill encounter beforehand. You want toavoid handling dangerous rocks andminerals. Galena (grey and very heavy)

and sulfur (usually BRIGHT yellow) shouldonly be handled with gloved hands.

Finally, leave the places you rockhound asyou found them. Pick up litter and debris;fill holes, respect landowners and otherswho use the area.


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zircon

4. WHERE IN THE MOHS IS IT?

By placing a rock within the MOHS scale, youare able to estimate the hardness of thatrock. This can be helpful in identifying astone.

When testing for MOHS, you dont need toscratch with all of your strength. Usingnormal pressure, like what you use when youare writing with a pencil, scrape the testingstone or tool across your rock.

Repeat this until your stone is scratched. Ifyour stone is special, dont use these tests, ordo them in an area you wont notice.

Fibrous malachite

5. LOOKS DO COUNT

Colour is extremely important in theidentification of many rocks. Once you haveseen the green of malachite you will alwaysremember it.

The appearance, or luster, of rocks is alsohelpful in their identification. Some will looksome will look dull like chalk (slate has achalk dullness), glassy like a drinkingglass (think of quartz or obsidian); greasy(graphite has a greasy feel); silky like silk(asbestos types look silky).

The mineral sample above is galena. This is a

toxic mineral you should avoid handling withbare hands. It, and lead, are noticeablyheavier than most rocks.

6. IT AINT HEAVY ITS JUST TALC

When you look in rock identification books,they usually provide the specific gravity (SG)of a rock or mineral. This is basically acomparison of the mineral or rock compared tothe weight of an equal volume of water. Waterhas a SG of 1.

Rocks that seem heavy for their size usually

have a high density. The density of a stonegenerally refers to how tightly packed thecrystals are. i.e. Galena has an SG of~7.4-7.6 and is quite dense, whereas sulfur weighsin at ~2-2.1 and isnt nearly as dense as thegalena.


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Common Streak Colours

Limonite = Yellow-brownHematite = Red-brownGold = yellowGalena = grey

Graphite = blackPyrite = blackMagnetite = blackChalcopyrite = black

Below are a couple of examples where knowingthe streak colour of stones can be quite useful.

The colour streak for gold is yellow and FoolsGold (Pyrite) has a red streak!

Hematite (a popular jewelry making stone) hasa read streak, while galena (a toxic stone withsimilar outward features) has a grey streak.

7. STREAKING IS ALLOWED

When it comes to rock & mineral identification streaking is allowed! In fact, it isencouraged! This is where the ceramic streakplates in your kit will come in handy.

To find out what colour streak your rock has,you will scratch it across both plates thewhite and the black unglazed ceramic.Sometimes youll be surprised, as the streakleft by a stone may be completely differentthan the colour of its actual physicalappearance! Minerals harder than the platewill not leave a streak.

It is important to note that most silicates(most of the stones we use in jewelry fall into

the silicate class) have a white streak and thismay not help identify them.

Rocks that contain calcium carbonate: Calcite (it IS calcium carbonate!) Limestone Marble (it is compressed limestone) Carbonatite Mexican Onyx Iceland Spar

8. POP, POP, FIZZ, FIZZNext we will play with the vinegar and thenail. This tiny experiment can help you findout if there is calcite (calcium carbonate)present in your rock. Calcite is one of themost common minerals on earth - ~4% of theearths crust (by weight).

Holding your rock firmly in your hand, scratchthe surface with either a pocket knife or thenail in your ID kit. If you cant scratch up alittle bit of shavings, you definitely donthave a rock that contains calcite.

Now, drop one drop of vinegar onto the pile ofshavings. If it fizzes, calcite is present. If itdoesnt, you probably dont have calcite inyour rock.

Some folks use Muriatic (hydrochloric) acid in

10% dilution for this test. Because Muriaticacid can be extremely dangerous to handle,its not something I suggest. HandlingMuriatic acid requires special training andhazard containment procedures.

Calcite can be the glue in: Sandstone Slate


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The rock above is the one well identify in this tutorial.

9. WHAT IS IT?Take out your first rock and give it a good look-over. You might already have a good idea if youare using a rockhound guide or map of deposits.

Can you tell if it is Igneous, Sedimentary orMetamorphic?

My s am p l e a t l e f t i s I g n e o u s i t l o o k s

l i k e i t c o o le d q u i c k l y b e c a u s e I d o n t s e ea n y s p e c i f i c cr y s t a l f o r m a t i o n s .

What kind of fracture or cleavage does it have?T h e f r a c t u r e s a r e c o n c h o i d al . W i t h m y

j e w e le r s l o u p e I ca n s e e l i t t l e d i sh e s

o r b o w l s h a p e s .

Where in the MOHS is this rock? Now well usethe MOHS scale to test my rock. Will #1 on theMOHS scale scratch it?N o

I n f a c t , t h i s s t o n e i s n t s cr a t c h e d u n t i l

w e g e t t o # 8 o n t h e MOHS sc a le . I t e s t ed

i t w i t h z i r co n a n d i t d o e s sc r a t ch m y

s t o n e . I a l s o d r a g g e d m y s t o n e a c r o ss

t h e g l a s s p l a t e , j u s t a l i t t l e p r e s su r e i s

n e c e ss a r y . I t s c r a t ch e d t h e p l a t e . N o w I

k n o w m y s t on e i s so f t e r t h a n # 9 .

I tried scratching it with my nail and couldnt getany shavings.

T h i s t e l ls m e t w o t h i n g s : 1 . I d o n t h a v e

c a lc iu m c a r b o n a t e p r e s en t i n m y r o c k

a n d m y r o c k i s h a r d e r t h a n t h e k n i f e s o

t h e MOH i s g r e a t er t h a n ~ 5 . 5 .

I know by observation that my stone is pink inappearance, as well as translucent and glassy. Ialso know that the area is known for quartz;specifically rose quartz is frequently found. I

looked in my mineral book and sure enough,everything matches up to rose quartz.

W i t h a l l o f t h e in f o r m a t i o n I n o w h a v e , I

k n o w t h a t m y s t o n e is r o se q u a r t z .

THANK YOU!

I hope this tutorial will help you identify some ofthe basic stones in your world. Remember, evenexperts have times when they cant identify arock specimen and need have it examined undera special microscope or have a chemical analysis.

The best way to learn aboutrocks is to meet with otherenthusiasts and explore asmany different stones aspossible. One of the bestways I learn about stones isthrough The Mineral of theMonth Club.

I wish you a future filledwith fascinating and

beautiful rocks and minerals!In my humble opinion, even

a plain old basalt river rock is gorgeous enough tobe used in making jewelry; in fact it is one of myfavourites!

For comments orquestions, please go toJewelryLessons.com

Please do not distributeor copy.

Copyrights 2008, Shelby Raymond, Skeena StormStones, http://skeenastormstones.com

All photos contained within this tutorial are theexclusive property of Shelby Raymond.

Map photo on page 5 is the property of theGovernment of Canada.
http://skeenastormstones.com/http://skeenastormstones.com/


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SUGGESTED REFERENCES

A Field Guide to the Identification of Pebbles. Eileen Van der Flier-Keller. HarbourPublishing.2006. ISBN-10:1-55017-395-2 (This is an AWESOME little reference for identifying riverrocks and regular stones!)

Rocks & Minerals. DK Publishing.2003. ISBN-13: 978-0-7894-9587-7Guide to Minerals, Rocks & Fossils. A.C. Bishop, A.R. Woolley, W.R. Hamilton. Firefly Books.

ISBN: 1-55407-054-6

National Audobon Society - First Field Guide: Rocks and Minerals. Edward Ricciuti, MargaretW. Carruthers. Scholastic Inc. 1998. ISBN: 0-590-0584-8

M i n e r a l o f t h e M o n t h Cl u b , http://mineralofthemonthclub.org(Please tell them Shelby Raymondreferred you! Thanks.)

T h e M i n e r a l a n d L o c a l it y D a t a b a s e , http://mindat.orgT h e P r a c t ic a l Ge o l o g i st : T h e i n t r o d u c t o r y g u i d e t o t h e b a s i cs o f g e o l o g y a n d t o c o l l e ct i n ga n d i d e n t i f y i n g r o c k s . Dougal Dixon. Raymond L. Bernor, Editor. Simon and Schuster, Fireside.1992. ISBN-13: 978-0-671-74697-1

Am e t h y s t Ga l l e r i e s ' M i n e r a l Ga l l e r y , http://mineral.galleries.com/

Disclaimer: Caution is urged while working with rocks and minerals. Children should always be supervisedby a responsible adult. Shelby Raymond and Skeena Storm Stones are not liable for accidents, injuries orlosses that may be incurred by use of this tutorial.
http://mineralofthemonthclub.org/http://mindat.org/http://mineral.galleries.com/http://mineral.galleries.com/http://mindat.org/http://mineralofthemonthclub.org/

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