Simple Geology Part 2: A Glossary of Terms,by Stephanie Pflumm ©Copyright 2007

[Guest guest]

Simple Geology Part 2: A Glossary of Terms

by Stephanie Pflumm ©Copyright 2007

we have received permission to repost articles by Stephanie Pflumm

 

 

Perhaps the most daunting part of learning geology for me was understanding

all the new words. Even worse, when I looked up definitions I was confronted

with more unfamiliar terms and explanations. There are still times when I am

not sure I know what they mean and I stumble around looking for confirmation

that what I think is what was said.

 

In a continuing effort to simplify geology for you, here is my attempt to

translate the language. The following words show up again and again in

references for crystals and minerals. I hope these translations help make your

own research a little easier.

 

ACICULAR - crystals that look like needles, thin and sharp

 

ALTERATION - the original form of a crystal, mineral or rock is changed,

either physically or chemically resulting in a new mineral, crystal or rock

 

AMORPHOUS - rocks, minerals or crystals that don't have a crystal structure

 

AMPHIBOLES - Quartz relatives that often form rocks; includes actinolite,

hornblende, glaucophane and tremolite

 

ASTERISM - the illusion of a star across the surface of a gemstone, usually

caused by Rutiles (Titanium crystals) within the stone

 

BITUMINOUS ROCKS - minerals containing oil, asphalt or tar (one of the few

rock types that has a scent, though an unpleasant one)

 

BRECCIATED - broken into pieces then cemented back together, ususally by

Quartz

 

CHATOYANCY - the appearance of a brighter line that moves along the surface of

a gemstone; aka cat's eye

 

CLEAVAGE - how a stone breaks when struck, usually along a specific plane or

surface of the crystal

 

CONTACT METAMORPHISM - a change that takes place at or near the point where

magma comes in contact with a mineral

 

FLUORESCENCE - glows under ultra-violet light

 

GEODE - a hollow rock with crystals growing towards the center

 

HARDNESS - refers to how easily a crystal or gemstone can be scratched or

marred; This is a deceptive term, while Jades tend to be considered a soft

stone because the surface can be easily scratched, it actually is a very tough

crystal and strongly resists breaking. On the other hand, Diamonds which are

considered the hardest of the gemstones can actually be very brittle and break

easily. See the term TENACITY for more information.

 

HYDROTHERMAL ALTERATION - minerals that are changed by super mineral rich,

very hot fluids, usually water

 

HYDROTHERMAL METAMORPHISM - changing of one crystal into another through hot

fluids

 

HYDROTHERMAL REPLACEMENT - changes caused by the replacement or removal of

minerals through hot fluids

 

IGNEOUS ROCK - stones formed when molten magma solidified

 

INCLUSION - a solid, liquid or gas inside a crystal

 

LAMELLAR/LAMELLAE - thin crystal layers or plates that affect the play of

light on a crystal (Labradorites and Moonstones are examples of crystals that

are lamellar)

 

LUSTER/LUSTRE - how light is reflected off the surface of a stone or crystal

 

MAGMA - molten rock beneath Mother Earth's surface

 

MAGMATISM - the process of turning liquid magma into stones

 

MATRIX - the rock or stone that a crystal grows on

 

METAMORPHIC ROCK - a rock that is turned into a different stone through heat,

pressure or the affect of hydrothermal fluids

 

MICROCRYSTALLINE ROCK - a stone with crystals too small for the naked eye to

see; most Jaspers and Onyx are microcrystalline

 

NODULAR - rounded crystal shapes; i.e. boytroidial

 

OXIDIZED ZONE - the area of a mineral that was changed by percolating

groundwater containing dissolved oxygen and carbon dioxide molecules

 

PEGAMATITE - an igneous rock that is a fertile breeding ground for numerous

crystals, they often form as dikes that can be several feet in length;

Moonstone, Quartz, Rose Quartz, Tourmaline and Mica are just a few of the many

crystals that can be found in pegamatites

 

PETROGRAPHY/PETROLOGY - the study, description and classification of rocks

 

PHOSPHORESCENCE - glows in the dark; not to be confused with fluorescence

 

PIPE - sort of like a pegamatite, except that it is vertical and shaped like a

cylindar; Sapphires and Diamonds form in pipes

 

PRECIPITATION - when refering to minerals, it describes the process of

dissolved or suspended elements evaporating or being separated from a liquid

 

PSEUDOMORPH - a mineral that takes the form or shape of a different mineral

 

REPLACEMENT - what happens when one mineral takes the place of another, as in

Petrified Wood where Quartz replaces organic material; the new mineral often

keeps the shape and appearance of the original

 

SEDIMENTARY ROCK - stones formed as sediment turns solid; sediment can be made

up of minerals, rock debris, animal or vegetable matter

 

STREAK - when a gemstone or crystal is rubbed across the surface of unglazed

porcelain it will leave a powdery streak, streak refers to the color left

behind

 

STRIATIONS - vertical, parallel groves on the surface of a crystal; Tourmaline

crystals are striated

 

TENACITY - how strong a crystal holds together; not the same as hardness -

Jades are very tenacious, Diamonds are not

 

TWINS - multiple terminations (points) growing from the same base crystal; (as

a mother of twins, I am especially fond of these types of crystal formations)

 

VITREOUS - the surface of the stone looks like glass

 

This list does not include every single one of the terms used in geological

references, but these are certainly the ones you'll see most often. Also,

please note that these definitions are not " text book " . I have tried to state

definitions in the simplest terms possible, which would make some of them

unacceptable to a trained petrologist. So, again, please don't use them to try

and pass your geology class.

 

Abundant blessings,

Stephanie

 

--

Solarraven http://pjentoft.com/index.html

Spiritual Healing, Energy work, Reiki, Crystal Healing, Angels, Huna, skills for

the practical mystic , Digital Art