Home

Feature Article:

Career Planning
Career planning necessary to work out Career planning is one of those things you don’t learn about in school but what decisions you make with your career affect your future in more ways than one. No matter what choices you make regarding your...
...Read More



 

Madagascar corundums ( Sapphire & Ruby discovery )

Navigation

© 2004 gggems.com All rights reserved.


AL2O3
Sapphire found in a metamorphized limestone.

· Crystallographic properties of corundum:
Trigonal.c = 1,3630 pp 0 86°4' ; pa1 = 122°26'
Macle according to p (1011), often polysynthetic,
accompanied by plans of separation, similar plans are also
observed according to a1 (0001) unequal break to conchoïdal.

Hardness 9. Density 3,95 to 4,1 Refractive index: 1.76 - 1.77
Uniaxial and optically négative.ng = 1,7675; Np = 1,7593
The faces a1 frequently show the phenomenon of asterism,
generally due to reflexions within separation p.
Strong polychromatism , with following maximum ng.
· Chemical properties: corundum is composed of pure
alumina; its colouring is due to metallic oxide traces or inclusions.
The color of sapphire, due to iron and titanium oxide, gives its best
effect under daylight. Electric light makes it often dark.
The color of the ruby, due to chromium oxide, on the contrary shows
its most luminous red under electric lighting.

The Corundum shows in Madagascar two different aspects:
1 stony and opaque crystals.
2 crystals of smaller size often transparent and usable as gem.
In Madagascar, stony corundum comes from mica schists metamorphized by granite, as well as
granitic veinules endomorphized and more or less deprived of quartz which injects those. Silimanite is a usual
satellite of corundum in this type of deposit. One also finds some in eruptive rocks, syenites. Gems are
generally found in alluvium, but come either from basaltic slags, or from metamorphized limestones or
endomorpheous feldspatic rocks.

1 2 3 4 5
One distinguishes two principal types of corundum in Madagascar:
Type I : isoceloedric, more or less acute accompanied or not by a small face a1 (0001) and more rarely by facets p
(1011). Represented by figures 1 to 11, but which often become complicated in consequence of the
irregularity of the development of some of their faces and by stacking with parallel axes of a great number
of individuals.

6 7 8 9 10

11 12
13

Scalenoedron Stacking with parallel axes, Crystal supporting on one of its bases
gutters at contours of the face. a small rhombohedron p in parallel position.

Type 2: Characterized by the association of the prism d 1 (1120) at a broad base, with which can associate the
isosceles ones, among which e 3 is most frequent, as well as the rhombohedron p.
The base of Malagasy corundum crystals very frequently shows scratches or triangular figures in relief,
limited by p.

Macle of blue corundum.
Translucent violet - pink sapphire


Ruby in amphibolite.

The crystals engaged in rocks, rich in mica have rough faces, encrusted of biotite or muscovite, minerals which
also exist at the state of inclusions, associated with magnetite and pyrite.
Because of its hardness, its inalterability and its density, corundum constitutes a standard mineral of alluvia.

Ruby Giant Sapphire in a metamorphic dolomitic limestone.


Polychrome Sapphire Blue Sapphire ( origin: Blue Sapphire ( origin: Ilakaka 1999 )
( origin: Iankaroka 1990 ) Andranondambo 1992 ) Found in the sandstones of Isalo in
This sapphire comes from a granit, The stone comes from alluvium, the shape is rounded.
its shape is intact. a metamorphized limestone. The origin of the stone is a limestone.


· The structure of crystals.
It is R.J.Haüy who put forth the first assumption, confirmed 200 years later, on the structure of the crystallized
material. He lets drop accidentally a calcite crystal which broke into small rhomboedrons. He supposed whereas
the crystals were consisted of stacking small rhomboedrons elementary (that he called the "integral molecule"),
he could reconstitute all known shapes of calcite. In a crystal lattice, three atoms or groups of atoms (nodes),
which is not on the same line, determine a plan called reticular plan. But there is a great number of these
plans: it is enough to choose nodes not strictly nearby. As the network is infinite, there is even an infinity of
possible plans. The dimension of the faces does not play of role. In the course of growth, a face can develop
more quickly than another. The angle that the faces make between them remains constant, since it
depend on the network. This structure of the crystalline material explains the law of the constancy of the

dihedral angles.

Triangular figure on a Scratches on a rare Stacking in macle Triangles on a translucent
colorless corundum. colorless corundum. of a ruby. corundum.

Triangular figure on a Triangles in step on a blue Remarkable macle of
blue corundum. corundum from Maromby. red corundum.
Sapphire & Ruby Safari Gem ruby from Ambatovaravarana.

The alluvial ruby deposit of Ambatovaravarana in the high plateaus, is in the
left center on the picture, under the hill.


Macle of blue sapphire. Macle of ruby 60 grms.

Information ¦ Cutting Styles ¦ Characteristics ¦ Crystalline Systems ¦ Madagascar Sapphire

Andranondambo Sapphires ¦ Blue Sapphire Crystal ¦ Ruby Crystal ¦ Sapphire Slice

Your guide to GGGems.com
All the pictures on this site have been shot by gggems.com Alain Darbellay

© 1987 - 2004 gggems.com All rights reserved.

About the Author

http://www.gggems.com/Madagascan_corundum.htm

 

More Reading:


TAKE THIS CAREER AND SHOVE IT IN THE RIGHT DIRECTION

Preschool Spanish

Do You Know Why Accreditation Is Important In E Learning

Give Your Child a Jump Start on Reading

Bolivia A Geographic Portrait

 
hexoctal music

Create a Rappin Resume

The Next Generation iBT TOEFL

Chiropractic Schools

Kids and Computing

Home

Business Search 
Business

Career
Internet-Marketing
Marketing

Additional Reading


Mysteries of Syndrome X Revealed
“I’ve put on 40 pounds in one year!” “It doesn’t matter how much I workout, I can’t lose weight.” “My doctor must think I’m eating pizzas in the closet.” With nearly 4 million Americans weighing in at over 300 pounds, is it any wonder the above...
...Read More

Coaching Employees - The Chronic Excuser
Most of us find coaching employees to be an effective, even enjoyable, approach to leadership and management. Coaching provides a way to help team members grow and develop, while achieving business objectives. But occasionally, we encounter a...
...Read More

Job Search Strategies that Work!
So you took your resume and posted it on the job boards. You also spent hours searching for the jobs that fit your background and career goals, and you responded to a few dozen jobs. Then you waited for the phone to ring. But it didn’t. What went...
...Read More

Culinary Arts School
I sometimes wonder why many people have the love for culinary arts. It seems everybody loves food and want to carve a career out of their love. Is it easy? Well, the answer is tough. A couple of months back I met a friend who is a software...
...Read More

Trying to Talk to Reach Teens? Maybe a Teen Quiz can Help
Q. I'm a new 8th grade teacher and I don't have a lot of experience with teens. Could you help me with a teen quiz that will get them thinking? A. Before I help you with a teen quiz, let me say "good for you"! Many new teachers start out in...
...Read More