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1dave
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Tourmaline Nov 2, 2015 13:18:55 GMT -5 nowyo, snowmom, and 4 more like this

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Post by 1dave on Nov 2, 2015 13:18:55 GMT -5

Tourmaline: any of a group of crystalline boron silicate minerals of complex composition, containing boron, aluminum, hydrogen, iron, lithium, magnesium, oxygen, potassium, silica, sodium, etc., usually black but having various colored, transparent varieties used as gems, but at 7 to 7.5, Schorl makes a very nice black stone.

Diamond has the simplest formula: C.
Tourmaline the most complex:
(Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6(BO3)3(Si,Al,B)6O18(OH,F)4

Its general formula can be written as

XY3Z6(T6O18)(BO3)3V3W,

where:

X = Ca, Na, K, ? = vacancy

Y = Li, Mg, Fe2+, Mn2+, Zn, Al, Cr3+, V3+, Fe3+, Ti4+, vacancy

Z = Mg, Al, Fe3+, Cr3+, V3+

T = Si, Al, B

B = B, vacancy

V = OH, O

W = OH, F, O

The tourmaline mineral group is chemically one of the most complicated groups of silicate minerals. Its composition varies widely because of isomorphous replacement as formation solutions changed, but ALL are Boron Silicates.

Because it can have so many variables in composition, it also takes many forms and colors.
The crystals often begin as triangles but end as hexagons. Often growing up as parallel rods then changing to tree like growth rings.

Possible

The 31 minerals in the group (endmember formulas) recognized by the International Mineralogical Association

Adachiite - CaFe2+3Al6(Si5AlO18)(BO3)3(OH)3OH
Bosiite - NaFe3+3(Al4Mg2)Si6O18(BO3)3(OH)3O
Chromium-dravite - NaMg3Cr6Si6O18(BO3)3(OH)3OH
Chromo-alumino-povondraite - NaCr3(Al4Mg2)Si6O18(BO3)3(OH)3O
Darrellhenryite - NaLiAl2Al6Si6O18(BO3)3(OH)3O
Dravite - NaMg3Al6Si6O18(BO3)3(OH)3OH
Elbaite - Na(Li1.5,Al1.5)Al6Si6O18(BO3)3(OH)3OH
Feruvite - CaFe2+3(MgAl5)Si6O18(BO3)3(OH)3OH
Fluor-buergerite - NaFe3+3Al6Si6O18(BO3)3O3F
Fluor-dravite - NaMg3Al6Si6O18(BO3)3(OH)3F
Fluor-elbaite - Na(Li1.5,Al1.5)Al6Si6O18(BO3)3(OH)3F
Fluor-liddicoatite - Ca(Li2Al)Al6Si6O18(BO3)3(OH)3F
Fluor-schorl - NaFe2+3Al6Si6O18(BO3)3(OH)3F
Fluor-tsilaisite - NaMn2+3Al6Si6O18(BO3)3(OH)3F
Fluor-uvite - CaMg3(Al5Mg)Si6O18(BO3)3(OH)3F
Foitite - ?(Fe2+2Al)Al6Si6O18(BO3)3(OH)3OH
Luinaite-(OH) - (Na,?)(Fe2+,Mg)3Al6Si6O18(BO3)3(OH)3OH
Magnesio-foitite - ?(Mg2Al)Al6Si6O18(BO3)3(OH)3OH
Maruyamaite - K(MgAl2)(Al5Mg)Si6O18(BO3)3(OH)3O
Olenite - NaAl3Al6Si6O18(BO3)3O3OH
Oxy-chromium-dravite - NaCr3(Mg2Cr4)Si6O18(BO3)3(OH)3O
Oxy-dravite - Na(Al2Mg)(Al5Mg)Si6O18(BO3)3(OH)3O
Oxy-schorl - Na(Fe2+2Al)Al6Si6O18(BO3)3(OH)3O
Oxy-vanadium-dravite - NaV3(V4Mg2)Si6O18(BO3)3(OH)3O
Povondraite - NaFe3+3(Fe3+4Mg2)Si6O18(BO3)3(OH)3O
Rossmanite - ?(LiAl2)Al6Si6O18(BO3)3(OH)3OH
Schorl - NaFe2+3Al6Si6O18(BO3)3(OH)3OH
Tsilaisite NaMn2+3Al6Si6O18(BO3)3(OH)3OH
Uvite - CaMg3(Al5Mg)Si6O18(BO3)3(OH)3OH
Vanadio-oxy-chromium-dravite - NaV3(Cr4Mg2)Si6O18(BO3)3(OH)3O
Vanadio-oxy-dravite - NaV3(Al4Mg2)Si6O18(BO3)3(OH)3O

Species:
Schorl May account for 95% or more of all tourmaline in nature.

Schorl - “Iron Tourmaline.” Brownish black to Black Schorl. The sodium iron (divalent) endmember of the group.
Environment Most often in granite pegmatites; also in skarns.
Rock Type Igneous, Metamorphic

Schorl01

Aquamarine xls on Schorl

Dravite species: named from the Drava river district of Carinthia

Dravite - “Brown Tourmaline,” Dark yellow to brownish black. The sodium magnesium rich tourmaline endmember. NaMg3(Al,Mg)6B3Si6O27(OH)
Dravite forms multiple series with other tourmaline members, including schorl and elbaite.
Dravite varieties include the deep green chromium dravite and the vanadium dravite.
Environment In marble deposits of metamorphosed limestone, metamorphic schists, and in mafic igneous rock and pegmatites. Rock Type Igneous, Metamorphic

Elbaite species: named after the island of Elba, Italy

Elbaite occurs in lithium bearing granite with a formula similar to Na(Li1.5Al1.5)Al6(BO3)3[Si6O18](OH)3(OH).
It's colorful crystals are considered to be the most valuable.

Watermelon Elbaite:

watermelonTourmaline

Achroite variety - Colorless (from the Greek meaning "colorless")

Indicolite variety - Light blue to bluish green—Brazilian(from indigo) Color is probably influenced by copper (azurite).
Magnetic blue tourmaline is colored by iron.

Rubellite variety - Red or pinkish-red (from rubellus) Color of by tourmaline crystals with Mn2+ were initially very pale. Due to natural gamma ray exposure from radioactive decay of 40K in their granitic environment, gradual formation of Mn3+ ions occurs, which is responsible for the deepening of the pink to red color.

Verdite variety - Green or Brazilian emerald Color is probably influenced by copper (malachite).

Environment Almost exclusively in granite pegmatites. Rock Type Igneous

Liddicoatite is an uncommon form of Tourmaline, almost identical in chemical composition to Elbaite, but with a calcium atom replacing a sodium atom in its chemical formula.

Liddicoatite watermelon crystals look a tad different.
LWC

Liddicoatite was not recognized as a separate Tourmaline species until 1977. Prior to that time, it was thought to be Elbaite. The original discovery of Liddicoatite in Madagascar was believed to be fully dominating in hydroxyl in its chemical formula. Subsequent analysis has determined a fluorine presence in place of some of the hydroxyl, though several localities (though not the type locality) do in fact contain all hydroxyl and no fluorine. The fluorine-rich Liddicoatite is recognized as a distinct mineral species by the IMA, and termed Fluor-liddicoatite. Liddicoatite is name after Richard T. Liddicoat (1918-2002), a well-known gemologist who was the president of the GIA, and inventor of the Diamond grading system.
Chemical Formula Ca(Li,Al)3Al6(BO3)3Si6O18(OH)4
Composition Basic calcium lithium aluminum boro-silicate, sometimes with fluorine partially replacing the hydroxyl
Color Liddicoatite is a very colorful mineral. Colors include green, red, pink, purple, and and blue. White, colorless, black, brown, yellow, and orange colors also exist. Crystals are frequently multicolored, containing two or more distinct colors. Liddicoatite may also have internal color zoning and banding. Some specimens are pleochroic.
Environment In lithium-rich granite pegmatites, and in placer deposits nearby the granite pegmatites. Rock Type Igneous
- See more at: www.minerals.net/mineral/liddicoatite.aspx#sthash.NUnWlLqv.dpuf

Uvite is a calcium magnesium tourmaline. The name Uvite is derived from the type locality of the Uva Province, in Sri Lanka, where it was first identified.

Uvite on Quartz

Color Light to dark green, light to dark brown, reddish brown, red, purple, brownish-yellow, white, gray, black. May also be multicolored with light and dark brown streakings.
Environment In metamorphosed Magnesite deposits, and in metamorphic skarns and marbles.

Color
Tourmaline has a variety of colors. Usually, iron-rich tourmalines are black to bluish-black to deep brown, while magnesium-rich varieties are brown to yellow, and lithium-rich tourmalines are almost any color: blue, green, red, yellow, pink, etc. Rarely, it is colorless. Bi-colored and multicolored crystals are common, reflecting variations of fluid chemistry during crystallization. Crystals may be green at one end and pink at the other, or green on the outside and pink inside; this type is called watermelon tourmaline. Some forms of tourmaline are dichroic, in that they change color when viewed from different directions.

The pink color of tourmalines from many fields is the result of prolonged natural irradiation. During their growth, these tourmaline crystals incorporated Mn2+ and were initially very pale. Due to natural gamma ray exposure from radioactive decay of 40K in their granitic environment, gradual formation of Mn3+ ions occurs, which is responsible for the deepening of the pink to red color.

Tourmaline is found in granite and granite pegmatites and in metamorphic rocks such as schist and marble. Schorl and lithium-rich tourmalines are usually found in granite and granite pegmatite. Magnesium-rich tourmalines, dravites, are generally restricted to schists and marble. Tourmaline is a durable mineral and can be found in minor amounts as grains in sandstone and conglomerate, and highly weathered sediments.

.. on the Money: Himalayan Tourmaline Mine Trip Gem Dig in California

Last Edit: Apr 4, 2019 21:04:58 GMT -5 by 1dave

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Tourmaline Nov 3, 2015 12:46:08 GMT -5

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Post by 1dave on Nov 3, 2015 12:46:08 GMT -5

Last Updated: 19th Apr 2009
Reprinted from: Gems & Precious Stones. Mineral Resources U.S., 1916, Part II - Nonmetals. Department of Interior, US Geological Survey, Government Printing Office, Washington; pages 896-898; 1919.
EXHIBIT OF TOURMALINE AND OTHER GEM MINERALS IN THE PEGMATITES OF SOUTHERN CALIFORNIA By Waldemar T. Schaller

The gem-bearing pegmatite region of southern California has been somewhat intensively studied by the writer under the joint auspices of the United States National Museum and the United States Geo―logical Survey, and an exhibit representing the region has been deposited in the National Museum, Washington, D. C.

The gems are contained in one case which has three horizontal shelves and two sloping shelves. The exhibit consists of specimens of the country rocks (granite and gabbro) and of their associated pegmatite dikes, in which are found the gem tourmalines and other gem minerals. The collection is shown on the first floor, main hall, east end, of the new National Museum Building, Washington, D. C.

The nearly flat-lying pegmatite dikes, from which most of the specimens shown were obtained, crop out on the hills north and east of Pala, San Diego County, Cal., and are of the compound, unsymmetrical type whose different parts are thought to be due to differentiation processes rather than to multiple injections of material into reopened fissures. The upper portion of the dike is locally known as the "top rock" and is a mixture of a coarse, granular aggregate of quartz and feldspar and of a graphic pegmatite. No gem stones are found in this "top rock." The lower portion of the dikes, locally called the "bottom rock," is a much finer grained granular quartz-albite rock characterized by numerous wavy bands of brownish-red garnets. These bands lie nearly horizontal in their general trend, being parallel to the slight dip of the dike. The "bottom rock" is likewise free from gem stones, but both it and the "top rock" are of great interest from the scientific point of view. Between the "top rock" and the "bottom rock" is the middle portion, called the "pay streak" by the miners, in which the gem minerals of value are found. Here also occur the cavities or pockets which often yield an abundance of the well-crystallized minerals shown in the exhibit.

The top horizontal shelf on the south side of the exhibit case contains the granitic and gabbro country rock, and also the partly altered gabbro—a loose, friable rock—and the completely altered gabbro, which as a brown iron-stained clay has been washed into the cracks and seams of the pegmatite rock. Where such a crack extends into a pocket the clay has coated the gems and associated minerals found therein. There are shown, for example, white feldspars of the pegmatite coated with the brown clay derived from the gabbro country rock. The origin of the clay of the gem pockets is thus explained.

The second horizontal shelf on the south side contains different varieties of the "top rock," consisting of graphic pegmatite and granular pegmatite. The third horizontal shelf shows the mineral aggregates of the middle part or "pay streak," which yields on decomposition the loose, friable material forming the gem pockets. This same shelf also shows examples of the banded "bottom rock."

The sloping shelf on the south side contains large specimens of the different varieties of the pegmatite rock, including granular, graphic, and banded pegmatites. Several of these larger specimens have been sawed and polished and are well adapted for use as an ornamental stone, especially when cut obliquely so as to form wavy lines and circular effects resembling bird's-eye wood. One specimen in particular consists of a large section of the entire pegmatite dike and shows the aggregate of lithium minerals in the upper portion or "top rock," the granular pegmatite of the middle portion, and the banded "bottom rock."

The sloping shelf on the north side of the case illustrates the mineral contents of the gem pockets. A sample of the gem-bearing clay or pocket material is first shown, below which is an equal amount of similar gem clay separated into its constituent minerals; thus the relative proportions of the gem tourmaline, the clay washed into the pocket from the decomposed gabbro country rock, and the various minerals associated with the gem tourmaline are exhibited. For example, the pocket material from the Tourmaline King mine, at Pala, shows much lepidolite, orthoclase, clay, and gem tourmaline (pink and green), and smaller amounts of muscovite and quartz. Similar gem-bearing clay from the Tourmaline Queen mine, at Pala, shows in addition to much pink tourmaline, large amounts of clay, quartz, albite, and cookeite, but practically no orthoclase. A gem pocket from the Ed Fletcher Jr. mine, at Pala, shows in addition to much pink tourmaline, clay, and albite, a considerable amount of lepidolite, with only a little orthoclase. A gem pocket from the Pala Chief mine, at Pala, shows considerable gem kunzite, with lepidolite, quartz, clay, cookeite, and orthoclase, and smaller amounts of albite and muscovite. A similar pocket from the Caterina mine at Pala, shows only spodumene, pink clay, and quartz. The exhibit also includes a pocket containing an abundance of small blue tourmalines; a small pocket from the Tourmaline King mine, very rich in gem tourmalines; and several pockets free from any gem stones. Such pockets are known by the miners as "dead ones."

On this same sloping shelf are shown also several large specimens of the minerals associated with the gem pockets. Among these minerals may be noted a fine example of orbicular muscovite, an altered perthite (feldspar) crystal, a large amblygonite crystal, and several specimens of spodumene (kunzite) in the matrix. These kunzite specimens are very difficult to collect, as in general the matrix of the kunzite is so friable that it breaks to pieces when it is taken out of the mine.

The three horizontal shelves above the sloping shelf on the north side of the case contain well-developed and well-crystallized specimens of the different minerals found in the gem-pocket zone of the pegmatite dikes. Among these minerals may be noted in particular a good series of the various forms of lepidolite (including several well-crystallized specimens), crystals of muscovite, fine tourmaline crystals, albite and orthoclase in well-developed crystals, pink beryl, stilbite, cassiterite, a large crystal of lithiophilite, bismuth, bismuthite, bismuthosphaerite, purpurite, hematite and pyrite, apatite, pucherite, topaz, manganotantalite, a fine example of clear pink kunzite in the matrix, and the phosphate minerals first found in this locality, namely, palaite, salmonsite, and sicklerite.

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1dave misunderstood rock expert Awed by the Universe! Member since October 2013 Posts: 11,948	Tourmaline Nov 3, 2015 12:48:54 GMT -5 snowmom likes this Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by 1dave on Nov 3, 2015 12:48:54 GMT -5 Anyone able to provide photos of the above?
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1dave
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Tourmaline Jan 15, 2018 8:59:59 GMT -5

Quote

Post by 1dave on Jan 15, 2018 8:59:59 GMT -5

What causes Tourmaline to change from linear growth patterns to radial growth and back ?
I have yet to find the answer.

From Mindat:

The structure for the group is one in which SiO4 tetrahedra are linked into six-membered rings having a hexagonal pattern and are stacked up with intervening distorted triangular BO3 groups, linked by D site cations;

the SiO4 tetrahedra are linked vertically by G site cations and X site anions,

while the columns are linked horizontally by both D site cations and X site anions.

The A site cations and the Z site anions occupy the channels down the centre of the columns (or the A site may be vacant). Additionally, tetrahedral boron ([4]B) may be present in both natural and synthetic tourmalines (Kutzschbach et al., 2016).

en.wikipedia.org/wiki/Tourmaline
Physical properties
Crystal structure
Tri-color elbaite crystals on quartz, Himalaya Mine, San Diego Co., California, US

Tourmaline is a six-member ring cyclosilicate having a trigonal crystal system. It occurs as long, slender to thick prismatic and columnar crystals that are usually triangular in cross-section, often with curved striated faces. The style of termination at the ends of crystals is sometimes asymmetrical, called hemimorphism. Small slender prismatic crystals are common in a fine-grained granite called aplite, often forming radial daisy-like patterns. Tourmaline is distinguished by its three-sided prisms; no other common mineral has three sides. Prisms faces often have heavy vertical striations that produce a rounded triangular effect. Tourmaline is rarely perfectly euhedral. An exception was the fine dravite tourmalines of Yinnietharra, in western Australia. The deposit was discovered in the 1970s, but is now exhausted. All hemimorphic crystals are piezoelectric, and are often pyroelectric as well.
Color
Tourmaline gemstones – Mozambique

Tourmaline has a variety of colors. Usually, iron-rich tourmalines are black to bluish-black to deep brown, while magnesium-rich varieties are brown to yellow, and lithium-rich tourmalines are almost any color: blue, green, red, yellow, pink, etc. Rarely, it is colorless. Bi-colored and multicolored crystals are common, reflecting variations of fluid chemistry during crystallization. Crystals may be green at one end and pink at the other, or green on the outside and pink inside; this type is called watermelon tourmaline. Some forms of tourmaline are dichroic, in that they change color when viewed from different directions.
Two dark green rectangular tourmaline stones and one oval tourmaline stone.

The pink color of tourmalines from many localities is the result of prolonged natural irradiation. During their growth, these tourmaline crystals incorporated Mn2+ and were initially very pale. Due to natural gamma ray exposure from radioactive decay of 40K in their granitic environment, gradual formation of Mn3+ ions occurs, which is responsible for the deepening of the pink to red color.[13]
Magnetism

Opaque black schorl and yellow tsilaisite are idiochromatic tourmaline species that have high magnetic susceptibilities due to high concentrations of iron and manganese respectively. Most gem-quality tourmalines are of the elbaite species. Elbaite tourmalines are allochromatic, deriving most of their color and magnetic susceptibility from schorl (which imparts iron) and tsilaisite (which imparts manganese).

Red and pink tourmalines have the lowest magnetic susceptibilities among the elbaites, while tourmalines with bright yellow, green and blue colors are the most magnetic elbaites. Dravite species such as green chromium dravite and brown dravite are diamagnetic. A handheld neodymium magnet can be used to identify or separate some types of tourmaline gems from others. For example, blue indicolite tourmaline is the only blue gemstone of any kind that will show a drag response when a neodymium magnet is applied. Any blue tourmaline that is diamagnetic can be identified as paraiba tourmaline colored by copper in contrast to magnetic blue tourmaline colored by iron.[14]

Last Edit: Jan 15, 2018 9:10:12 GMT -5 by 1dave

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Tourmaline Jan 15, 2018 9:23:40 GMT -5

Quote

Post by 1dave on Jan 15, 2018 9:23:40 GMT -5

Perhaps THIS will provide the answers I seek:

Tourmaline - Fascinating Crystals with Fantastic Inner Worlds

By Paul Rustemeyer
(2015) 272 pp, hardbound, size 22 x 29 cm, weight 1,8 kg, more than 650 figures, written in English and German. ISBN 978-3-89937-194-9; 9783899371949; US$90.00

Tourmaline crystals are not only much sought after gemstones but also are highly interesting as study objects, because on them the formative forces in the mineral kingdom create an impressive richness of shapes and colors. Especially the research of the inner of dark or even black crystals is very exciting. When slices of such crystals are ground thinner, beautiful fine structures appear out of the dark. This is the way in which fantastic and detailed picture worlds have been discovered; they are presented in this book as TourmalineArt and put into a natural scientific framework, but which is generally understandable.

The author has been dealing for more than 20 years with the aesthetics of the color pattern and their mineralogical interpretation; he put together the very best and most interesting of thousands of crystals in this book. The fantastic photos of the hidden structures within tourmalines make this book a feast for the eyes also for the lay public.

Table of Contents

Preface
Introduction
The Structure of Tourmalines
The Colour Palette of the Tourmalines
The Growth of Tourmaline Crystals
The Structures of Crystal Forms
Rim Structures
Delta Structures
Trigonal Dislocations
Division into Parallel Aggregates
The Healing of Broken Tourmalines
Naturally Corroded Tourmaline Crystals
Healing of Corroded Tourmalines
Healed Corrosion of Cavities
References

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1dave misunderstood rock expert Awed by the Universe! Member since October 2013 Posts: 11,948	Tourmaline Jan 15, 2018 9:36:20 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by 1dave on Jan 15, 2018 9:36:20 GMT -5 Perhaps not.
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orrum gets rocks for Christmas Member since January 2013 Posts: 7,205	Tourmaline Jan 15, 2018 10:37:48 GMT -5 via mobile 1dave likes this Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by orrum on Jan 15, 2018 10:37:48 GMT -5 Good article Dave! I have some schorl black tourmaline I got from the Hogg Mine in LA Grange Ga. I thought it was too soft to cut, must needs rethink that now! Thanks pardner!!
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Deleted Deleted Member Member since January 1970 Posts: 0	Tourmaline Jan 15, 2018 10:49:39 GMT -5 via mobile 1dave likes this Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by Deleted on Jan 15, 2018 10:49:39 GMT -5 Jan 15, 2018 9:36:20 GMT -5 1dave said: Perhaps not. Recently, I needed a book. $400!! Google was my friend. I found a full PDF of the book for download, free!

1dave misunderstood rock expert Awed by the Universe! Member since October 2013 Posts: 11,948	Tourmaline Jan 15, 2018 11:56:35 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by 1dave on Jan 15, 2018 11:56:35 GMT -5 Has anyone tried black tourmaline for backing doublets or triplets?
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1dave misunderstood rock expert Awed by the Universe! Member since October 2013 Posts: 11,948	Tourmaline Apr 4, 2019 12:51:26 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by 1dave on Apr 4, 2019 12:51:26 GMT -5 "Mysterious and changing Tourmaline" by Roger Warin - (29) www.mineral-forum.com/message-board/viewtopic.php?t=5617&sid=043b3b2d4351999859c30e918bc1f968
	Last Edit: Apr 4, 2019 12:55:37 GMT -5 by 1dave I'm a ROCKOLOGIST ! My Published Books: 1936dave.freeforums.net/

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Tourmaline Apr 4, 2019 17:20:26 GMT -5 1dave likes this

Quote

Post by gemfeller on Apr 4, 2019 17:20:26 GMT -5

I can tell you one thing from a purely non-technical point of view. A lot of tourmaline xls are under a lot of internal strain. They're prone to developing fractures along the a-b axis when the strain is relieved during the cutting process. Some will actually pop in half. Others will look perfect after cutting but will fracture days or weeks or months after cutting.

A lot of cutters claim that "skinning" the xls prior to faceting (gently grinding off the outer layer) stabilizes them for cutting. It's one of my very favorite gemstones due to the variety and beauty of its many colors, but it can sometimes be frustrating to facet.

I have quite a few bicolored Pala stones if those are what you wanted pictures of 1dave. They're hard to photograph but I'll give it a try. I have lots of really nice cabs from Brazil and other areas as well.

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Tourmaline Apr 4, 2019 20:57:42 GMT -5

Quote

Post by 1dave on Apr 4, 2019 20:57:42 GMT -5

Apr 4, 2019 17:20:26 GMT -5 gemfeller said:

I can tell you one thing from a purely non-technical point of view. A lot of tourmaline xls are under a lot of internal strain. They're prone to developing fractures along the a-b axis when the strain is relieved during the cutting process. Some will actually pop in half. Others will look perfect after cutting but will fracture days or weeks or months after cutting.

A lot of cutters claim that "skinning" the xls prior to faceting (gently grinding off the outer layer) stabilizes them for cutting. It's one of my very favorite gemstones due to the variety and beauty of its many colors, but it can sometimes be frustrating to facet.

I have quite a few bicolored Pala stones if those are what you wanted pictures of 1dave . They're hard to photograph but I'll give it a try. I have lots of really nice cabs from Brazil and other areas as well.

I would love to see them!

I would like to understand why they change from growing up to growing out.

Does a change in solutions change the type of tourmaline being grown?

[img

Last Edit: Apr 4, 2019 21:15:13 GMT -5 by 1dave

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rocknrob:

Nov 20, 2024 21:54:31 GMT -5

rocknrob: That was one heck of a windstorm that thankfully missed me. I guess Seatac almost hit 60mph gusts. I bet those were some fun landings Nov 20, 2024 21:55:16 GMT -5

rocknrob: I'll always love my pet rock, he's such a geode boy. Nov 22, 2024 9:27:33 GMT -5

RickB: