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Tonight's topic is Gems and Jewelry II: the Hard Ornamental Materials

Again as with the soft materials almost every colored stone has been used at one time or another for figurines, inlay, and other articles of display as well as jewelry so rather than try to cover all of them we are going to look at the most common and best known if you have a question about something that I don't cover please let me know and I'll see if I can find it in my resources also like before we will generally work our way up the values from the least expensive to the most. We will start with some Decorative Rock Types, then the Epidotes followed by Rhodonite, the Feldspars, the Quartzes (Chalcedonies, Massives, and Crystals), Lapis, and the Jades.

The first group for tonight are some rocks that we have mentioned in passing before that are sometimes colorful enough to be carved or cut and polished. these are:

{P} *dramatic pause*

*{P} hides... "Sorry" *sheepish grin*

a course grained contact metamorphic rock that has grains of silicates and calcareous minerals in pink browns, reds, and greens it is often banded and may contain geodes.

another contact metamorphic rock containing carbonates (Calcareous minerals), metal sulfides and oxides.

Calciphyre (Calc-silicates)
A third contact metamorphic rock that is generally light in color with labradorite and with pink, yellow, green, blue and black grains and zones or bands.

An extremely high grade metamorphic to igneous rock- especially high pressure ranging from green to red and course grained - the main minerals being garnet, pyroxene and quartz.

An igneous rock consisting of chrome diopside, pyrope garnet and accessories and having a course grained red to green color


Garnet Peridotite
Garnet (red Pyrope) and Peridot (olivine-green) generally medium grained peridot with large fractured garnets.


- there are 2 minerals and one rock in this group.

Clinoziosite Ca2AL3Si3O12(OH)
H) 6.5 D) 3.4 - it forms pink to pale green masses and the best massive material is found in Baja Calif.

Is the same material with a different crystal structure - it ranges from white thru pale blue to green and violet. A pink Manganese variety is known as thulite. While it is found in many places including Wyoming, Austria, the Urals and Kenya it is the Tanzanian deposits that are best known - these form rich green masses with red rubies.

{A} ooohhhhh rubies

A rock made of epidote (pistachio green) and pink feldspar - this is found in the southeast of the US and in Zimbabwe.

Any questions on these?

{P} Nuh uh :>

H) 5.5-6.5 D)3.4-3.7 is the pink Manganese Silicate - this is used instead of Rhodocrosite for things like wine cups and table tops that are subject to acids or abrasion since it is acid resistant and tougher and harder. The best pieces are marked with patterns of dark Manganese oxides that create incredible patterns against the pink background. The better material comes from Broken Hill Australia, Langban Sweden, Daghezeta Tanzania, Sverdlovsk Russia, and Honshu Japan. A darker zinc bearing variety is found at Franklin NJ.

any questions?

* P shakes her head...

<EW> not yet


Here there are 2 different groups the Potassium (K) Spars and the Plagioclase Feldspars.

Kspars are mostly white and nondescript but the low temperature variety called

Microcline can form in a number of other colors - the most common is pink - hence the pink color of Granites in many cases. The important version however is a chrome enhanced form called Amazonite or Amazonstone that is a bright green. The name comes from the fact the variety was first found in pebbles and stones in the Amazon river basin in Brazil - and much of the best material still comes from there. Other good locations are Amelia County VA and Pikes Peak CO - I have a number of fine small pieces from Amelia :>

Perthites are mixtures of Kspar and Plag that have formed intermixed twins and fine patterns. These fine layers and intermixed colors (pink and white-grey or green and white-grey) are very attractive and sometimes the layers and crystal twins will separate and reflect the light in patterns that are known as schiller. Amazonite and perthite are used to make jewelry (cabachons) and to make things like figurines and cups and containers - essential anything you might carve. They are usually opaque so the are seldom carved into thin or extremely hollow objects - like Jade is. The best Perthites come from Dungannon Ontario. So some nice stuff up your way P and some of your oldest stuff <G>

{P} :>

Plagioclase is actually a solid solution of two minerals: albite (sodium Plag) and anorthite (calcium plag) that form microscopic twins. When these two types are in almost even amounts we have the type known as Labradorite.

Then the twins are evenly split between the two minerals creating a multitude of tiny reflective planes that create a schiller in blue and green and sometimes gold. When there are inclusions of hematite this material changes slightly to show a gold to red schiller and color that is known as Sunstone.

Labradorite is named for Labrador Canada where huge masses are found. In fact these rocks are almost pure feldspar and some of the oldest rocks found (3.2-3.5 BY) and are called Anorthosites. The best sites for Sunstone are Tvedestsand and Hittero Norway and the Harts Range N. Territory Australia. Anorthosite and labradorite are found in Labrador (surprise surprise :>), several other sections of the Canadian shield and the Adirondacks of NY. Some is also found in Greenland adjacent to Labrador.

{A} the way it looks I almost expect it to feel greasy (I know sounds dumb but it looks like it to me)

Yes and for almost the same reasons as the oil - the microscopic twin planes split the light by sizes and reflect only selected colors and since they are not all the same distance. between the colors vary. At the American Museum in NYC there are several large (3 ft) slabs on display that are incredible. Oh - these materials are more normally used for things like table tops and inlay than for figurines and containers.

any questions?

{P} Nope :>

{EW} no

{A} what makes it reflect the gold or yellow colors so ... well tis almost glowing looking that is the reflection off of microscopic plates of hematite - iron oxide. and it tends to give it a reddish or yellowish color

{A} aaaahhhhh, k

{EW} ok :)

ok next group - everyone ready?

{P} Yep :>

{EW} yea

Anorthosite was already described, and the last is Larvikite also known as alkaline feldspar syenite and like Anorthosite its dominant mineral is labradorite - but it is richer in dark minerals and sulfides than anorthosites.

any questions?

{P} Nope :>

{EW} is there a picture of that last one?

yes there will be <G>

{A} no questions on thi


the quartz family can be split into 3 subfamilies:

Chalcedonies (cryptocrystaline quartzes (super microscopic crystals) )

Massive or microcrystaline quartzes

Crystal Quartzes

The general name for any crypto-quartz is Chalcedony. This name comes from Ancient Chalcedon in Asia Minor (Turkey) where it was once mined along with copper (where the name actually comes from). Chalcedony ranges from translucent to opaque and every color from white to black is possible. The main varieties are:

Onyx - pure white or pure black or alternating bands of black and white. Onyx comes from the Greek word for nail or claw

Sard - a pure blood red (and Sardonyx bands of sard and onyx), Sard is named for Sardis also in Turkey

{EW} I don't know there was white onyx

sure is sons and I have some nice Easter eggs of it <G>

{P} I didn't even know that Onyx was a quartz... heh

{EW} I thought they are made of alabaster?

The name has been used for both materials and that has created confusion - alabaster is much softer and should be kept separate - but because its soft and easy to cut and polishes to look like onyx it is often sold as it - welcome to gem faking 101 <G>

* *{S} grins.

*{A} grins


We will talk more about such things after covering the real things ok?

{EW} ok :)

*{A} wonders if DH has the red on his web site? Tis not in my books (pic that is)


*{A} nods

No I don't hun - at least not yet

*{A} has not seen Sard before and is interested

Then I'll make a special effort to find a picture <G>

*{A} does not want to take up your time I can search next time I am on a pc at work :)

Carnelian - orange red from iron inclusions this variety is named after the Latin word for flesh which color it generally resembles. Carnelian is found on some English beaches but the majority of it and of sard and sardonyx now come from Brazil and Uruguay

Plasma is a dark opaque green due to inclusions of green silicates. if it is spotted with red-orange dots of iron oxides it is called Bloodstone. Plasma and Bloodstone come primarily from India and Brazil.

*{A} grins ... that's one of my all time fav stones. Tis vvvvpretty not to mention cool looking

A second name is Heliotrope for red reflections this material often produces when when turned to face the sun under water.

yes it is <G>

Chrysoprase is a translucent green chalcedony and gets its color from traces of nickel in it the best Chrysoprase comes from the Marlborough Mine in Queensland Australia other deposits are found in Silesia Poland.

{P} Lotsa industry there :> natural resources... at least that's what I was told...

Agate (named fore the Agate river in Sicily) is any chalcedony that is layered or banded with several colors or bands or that contains dendritic (root like) inclusions (normally of manganese) a large number of varieties are named - mostly on the bases of the patterns of the colors and dendrites.

Chert and Flint are two other varieties of Chalcedony - chert being a light grey and generally translucent while Flint is a dark grey to black and more opaque.

Petrified Wood and some types of fossil bone are also chalcedony and are often polished (esp petrified wood) since they retain the cellular structure of the tree or bone both can be any type of the above materials thou carnelian and agates dominate. Agate is found in many places in the US and petrified wood and dinosaur bone are found in a number of places in the southwest and recently formed petrified wood can be found in Wyoming at Yellowstone (recently as in within the last 50 years <G>)

any questions on this group? or sub group :>

{A} um ... can you explain the last bit

Well I'll try to find the photo of it too but here goes :>

The geysers and hot springs of Yellowstone are rich in dissolved silica - as they cool the silica normally precipitates out to form the walls of the pools or the stream side formations but occasionally a spring will flood a forest region nearby as the hot mineral rich waters are absorbed by the wood of the trees they cool and react exchanging silica for carbon and replacing the cells of the trees - this kills the trees but the fluids are sucked up a ways creating a white base of petrified wood below the wood of the tree.

{A} aaahhhh.

{A} now that would be something to see.

When the tree top falls it then falls into these mineral rich waters and the reactions continue turning the entire trees into rocks in a matter of years.

<*{S}> Interesting... Did not know the process was that quick.

{P} Ohhhh, nifty :>

I'll scan a picture I have of this - they are called bobbysocks trees for fairly obvious reasons <G>

{EW} I didn't know it was that quick either

{P} Hehe :>

{A} does it have the colors like other petrified woods?

It can - and the same thing can happen to bones of animals that fall or are thrown/trapped into the springs. The trees are white on the outside - the colors will prolly come later as iron and other minerals are added slowly.

{A} true

ok any other questions?

{P} *noddles* My mother has a length of petrified wood... it's fairly dark... very brownish... lovely though :>It's one of the really old ones though...

yes they are I have several pieces of several different colors

{A} I have a nice piece too ... it has a "layer" of clear quartz xstals on the "bark" tis neat to the touch.

{S} DH, there is an area of the south west, I think they call it Painted Cliffs or something similar. It has a huge area of p wood and is very interesting... How would a forest of such size become saturated... It seems the springs would dry up or recede, or am I not thinking clearly... Is the eruption of the mineral water usually a continuous thing?

Its the Petrified Forest and it formed somewhat differently - here the trees were knocked down into a sandy swamp and buried. Then as waters flowed thru the sands they slowly replaced the wood with the silica - same basic process but the start is very different.

{A} what about the length of time?

Much longer - thousands to millions of years instead of years to thousands of years in Yellowstone. and we don't really know why the trees were all knocked down - or even if it was a single event or several close together.

Ok these quartzes are turned into almost anything you can imagine so I'm not going to try and list them all :>

Microcrystaline Quartzes - in these the crystal grains are almost visible rather than needing a high powered microscope to see.

Jasper is the first of these and is really just course grained Carnelian. It is found as the main ingredient in the banded ironstones of the Lake Superior region. Iron mines and other similar mines in Australia, Europe, and elsewhere. it is used in exactly the same ways as carnelian.

Aventurine Quartz contains scales and flakes of mica, hematite or goethite that give it a courser spangled green to brownish yellow look. The green variety of Aventurine is rich in the green chrome mica Fuschite and the best comes from India. A blue variety is rich dumortierite and very attractive also.

Quartz that has replaced fibrous actinolite is known as Tigerseye - the golden form is a complete replacement while the blue form retains some of the blue actinolite needles. The blue form (Falconseye) is primarily from South Africa.

And those are the microcrystaline quartzes any questions?

{P} No...

{EW} nope

{K} shakes head

Crystalline Quartzes:
these are actually carvings and figurines etc made from single crystals of Quartz. There are four varieties that are used with any real frequency:

Rock Crystal - clear Quartz.
The best known of the objects made from this are Crystal balls <G> but other objects are made. Good localities include Minas Gerais Brazil (xstals to 5 tons found), St. Gothard Switzerland, Malagasy Republic, Tyrol Austria, Arkansas (near Magnet cove) and many other places world wide.

Rose Quartz
Most of this material is translucent but the best is transparent pink. The reason for the color is still not known. Pala CA, Newry Maine, and Minas Gerais are the best known localities but it is found in many pegmatites around the world.

This is a clear yellow variety and fairly rare - much of the commercial material is made from treated Amethyst.

The purple form. The color comes from iron mixed in with the quartz in trace amounts. The best amethysts are from Minas Gerais ( up to 12 inches long). Amethyst is found in many other places but crystals large enough to carve are rare. Geodes filled with amethyst are often cut and polished to turn them into display pieces or bookends and may have both agate and amethyst in them. Unusual Ghost amethysts are found in Amelia County VA - these have the outline of a deeper purple crystal visible inside a larger lighter crystal. Some Ghost Rock crystal is also found here.

any questions on these?

{P} No... but it still ticks me off that sapphires don't' come in geode :>

*{A} thinks rubies and emeralds should too

Ah well hun

*{A} laughs

{EW} where is Minas Gerais?

Central Brazil - HW assignment for everyone - find a map of Brazil and find the province of Minas Gerais - your going to be hearing a lot about it in the next couple of weeks so you might as well all find it <G>.

{P} Somewhere just behind my left elbow I think :>

*{P} grins at anna


{EW} LOL ;>

*{A} grins at Pangea

any more questions?

{P} Nope :>

{A} not on this

{EW} no

{K} nope

ok lets move on to the last three groups for tonight


Lapis-Lazuli (Lapis)
it is made of 3 different minerals and graded according to the which is dominate. These are Hauyne, Sodalite and Lazurite in increasing order of value.

Hauyne (Na, Ca)4-8(Al6 Si6)O24(So4,S)1-2
H)5.5-6 D)2.45 is never the primary mineral in Lapis but is often present in small amounts. It is a dark blue to green in color.

Sodalite Na4Al3(SiO4)3Cl
H)5.5-6 D)2.3 - It is a light to medium blue and normally forms granular masses. The best localities for it include Bancroft Canada and the Monteregion Hills of Quebec (one has section of almost pure Sodalite), Litchfield Maine, and Magnet Cove AK

Lazurite (Na,Ca)8(Al,Si)12O24(S,SO4)
H)5-5.5 D) 2.4 is the most valuable. It is a rich royal blue to purple in color. The Badakhshan Afghanistan deposit is the world's best and has been mined for over 6000 yrs.

*{P} was gonna buy a tube of ultramarine blue paint once [2 fl. oz.] it had real lapis-lazuli ground into it... was $100 a tube... eek - Yeah, it's expensive all right :>

Agreed :>

Other deposits are found at Mogok Burma, Siberia, Angola, Labrador, Pakistan, California and Colorado. Lapis is a massive material made of some combination of these minerals with flecks of pyrite (golden yellow) and calcite (white points and streaks/bands). and yes its very expensive -especially the true afghani material. The material from the Monteregion hills ranges from a light blue to a full deep blue and is fairly easy to work - I have a couple of small pieces I collected back in '77 still I think. Lapis has been formed into everything from chess pieces to thrones.

{A} thrones?

{P} Yeah, the Egyptians used it a lot no?

Ever hear of the Persian Peacock throne?

{EW} there was a lot of Lapis in king Tut's tomb

Yes there was

{EW} Shah of Iran?


{A} aaahhh yes

The throne is several hundred years old and partly made of Lapis

any other questions?

{P} Not me :>

{K} nope

{EW} no not from us


{K} oh I like jade ;>

Jade is actually 2 different minerals the massive fibrous form of the amphibole actinolite is known as Nephrite; he other is the Pyroxene Jadeite. Both are fibrous (microscopically to barely visible) tough, hard (H= 6-7), dense (D=3-3.5) minerals.

Jadeite is Na(Al, Fe)Si2O6
Jadeite is the rarer and more valuable while Nephrite is the typical early Chinese and American jade. Jadeite is found in Tawmaw Burma (which produces the finest known as Imperial Burmese), Tibet, Yunnan China, Guatemala, California and Japan.

Nephrite is a variety of Actinolite: Ca2(Mg, Fe)5(Si4O12(OH)2
Nephrite is found in Turkestan (Khotan, Kasgar, Yarkand), the Lake Baikal region Siberia, Wyoming, Taiwan, British Columbia, California New South Wales Australia, Zimbabwe, and New Zealand.

The colors for each range from pure white to pure black and every color in between. The colors generally get darker with increasing iron - but traces of other elements can create almost any color imaginable. One of the photos I'll be including is a lavender Jade dragon Vase from the Smithsonian Collection.

{EW} pink jade is pretty

{P} Ohhhh :>

Ok all of these are also used to make next week's topic - Cabochon Stones <G>

{P} WOOHOOO!!!! :>

{P} We're getting closer :>

yep and you will see your first rubies and sapphires next week <G>

*{P} nudges anna "We'll go to the next swap meet, steal all our birth stones, and then bugger off"

hmmmmm shall I do a special class on birth stones and such?

{P} Ahhh, now that would be interesting... I'd like to know about the history of why stones were chosen and such :>

*{A} has another question about the p wood in Yellowstone

Ok what is it hun?

{A} has anyone studied the process there and do they have any estimates at how long it takes?

Well the trees in the photo I'll put up (from 1989) were flooded about 8-10 years earlier and the main destruction was done within a year or two. The level of the top of the socks is still going up tho. anything else?

{EW} not from us

*{P} shakes her head...

Ok then shall we adjourn till next week?

{P} It's okay by me :>

Website created: January 22, 1998
Website last updated: October 11, 1998