Saturday, March 1, 2008

Violets are blue, and so are you: Amethyst!

Isn't that amazing that some minerals can be found in so many different forms, colors, varieties, locations and ore deposits? such is the case of Tectosilicate Quartz (SiO2), an old German / Saxony's word that meant ice very frozen.

Quartz is the most abundant mineral in the surface of the world, found in almost each and every type of rock, or by itself in geodes, or cavities in acidic volcanic lavas, or magmas. However, one of the prettiest of all quartz varieties is the purple or violet colored gemstone, known as "amethyst" a semi-precious stone beloved by many people, including me.

For a mineralogist, the value of an amethyst comes from its degree of crystallization, color and size. The deeper the color, the larger the size, and the most perfect its crystals are, among other features makes it more valuable, and even appreciated in a Museum of Natural History.

The name "Amethyst" comes from the Greek "amethos" or alcohol. The following story is not well known, but I learned it from Professor Raul Ortiz Asiain (for me, the best Mineralogist in Mexico of all times), that people that eat amethyst dust did not suffer of hang over after drinking heavily the night before. I never tried such a recipe, because first of all I don't drink; I haven't heard this anywhere else in the world, and Professor Ortiz Asiain passed away more than 10 years ago, rest in peace.

Anyhow, let us go technical:

Chemical Formula: SiO2
Molecular Weight = 60.08 gm
Environment: Sedimentary, metamorphic, and igneous rocks.
Locality: Very common mineral found world wide.
Name Origin: From the German "quarz", of uncertain origin.
From the same chemical formula:

Agate - Banded variety of chalcedony
Amethyst - Purple
Avanturine - Feebly translucent chalcedony
Carnelian - Flesh red chalcedony
Cat's Eye - Chatoyant
Chalcedony - Micro crystalline quartz
Chert - Crypto crystalline quartz
Chrysoprase - Apple green chalcedony
Citrine - Yellow
Flint - Micro crystalline quartz
Hornstone - Flint
Jasper - Red or brown chalcedony
Moss Agate - Variety of chalcedony
Plasma - Green chalcedony
Prase - Leek green chalcedony
Rock Crystal - Transparent
Rose Quartz - Rose colored
Sapphire Quartz - Blue colored
Smoky Quartz - Brown to black
Tiger Eye - Pseudomorph of asbestos

Crystal System: Trigonal - Trapezohedral
Cleavage: [0110] Indistinct
Color: Brown, Colorless, Violet, Gray, Yellow.
Density: 2.6 - 2.65, Average = 2.62
Diaphaniety: Transparent
Fracture: Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Habit: Crystalline - Coarse - Occurs as well-formed coarse sized crystals.
Habit: Crystalline - Fine - Occurs as well-formed fine sized crystals.
Habit: Druse - Crystal growth in a cavity which results in numerous crystal tipped surfaces.
Hardness: 7 - Quartz
Luminescence: Triboluminescent.
Luster: Vitreous (Glassy)
Streak: White

Ok, enough I think, by now I am sure you are an expert in Amethyst and its mother quartz. By the way, the only joke I remember about quartz goes like this: Dad (a little quartz talking to his father), is it true that we precipited out of solution? Dad answers: Of Quartz!

Have a terrific weekend, and in the meantime, you may want visit my website where you can find a nice picture of the day taken by me somewhere in the world with my nice Nikon D40X: Oscar el Mexicano

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