Thursday, November 26, 2009

Specimens with a beauty beyond this planet!

Magnificent specimens I am glad to welcome to my blog. These are jaw-dropping, breath-taking minerals, with a beauty beyond this world! Some of those are on sale by Exceptional minerals. The description of each mineral follows the order of the pictures:

Golden Calcite (CaCO3)crystal on Barite (BaSO4)from the Elmwood Mine, Smith County, Tennessee.

Gorgeous deep cherry-red Rhodochrosite (MnCO3) rhombs Trigonal - Hexagonal Scalenohedral with Quartz on Tetrahedrite matrix from the Millennium Pocket of the Fluorite raise, Sweet Home Mine in Alma, Colorado now closed.

The gold on quartz collected from the San Pedro Mine in Santa Fe county New Mexico is on sale for $45,000 USD, I am sure that the gold price of $1,160 US/oz fueled this price tag among its rarity and beauty, just affordable by affluent collectors, or by well funded museums.

Beryl var. Aquamarine (Be3Al2Si6O18)crystal sitting atop bronze Muscovite (KAl2(Si3Al)O10(OH,F)2)blades from Nagar, Aliabad, Hunza Valley, Northern Areas of Pakistan.

Grossular (garnet Ca3Al2(SiO4)3)), and Diopside (CaMg(Si2O6) from Val d'Aosta, Italy.

Thursday, September 10, 2009

Apatite / Apatita var. Esparriguina, what a name uh?

This is a beautiful mineral rarely found in good crystals, this particular one from the Market Hill (Cerro del Mercado) in Durango, state of Durango, Mexico. Variety of this pale yellow specimen is named "Esparriguina."

Apatite is actually three different minerals depending on the predominance of either fluorine, chlorine or the hydroxyl group. These ions can freely substitute in the crystal lattice and all three are usually present in every specimen although some specimens have been close to 100% in one or the other. The rather non-inventive names of these minerals are Fluorapatite, Chlorapatite and Hydroxylapatite. The three are usually considered together due to the difficulty in distinguishing them in hand samples using ordinary methods.

An irony of the name apatite is that apatite is the mineral that makes up the teeth in all vertebrate animals as well as their bones. Get it? Apatite - teeth! Anyway, the name apatite comes from a Greek word meaning to decieve in allusion to its similarity to other more valuable minerals such as olivine, peridot and beryl.

Apatite is widely distributed in all rock types; igneous, sedimentary and metamorphic, but is usually just small disseminated grains or cryptocrystalline fragments. Large well formed crystals though can be found in certain contact metamorphic rocks. Very gemmy crystals of apatite can be cut as gems but the softness of apatite prevents wide distribution or acceptance of apatite as a gemstone.

Let's go technical:
Chemical Formula: Ca5(PO4)3(OH,F,Cl)
Name Origin: Named in 1788 from the Greek apatao - "I am misleading." Reason is that it mislead to confuse for some valuable minerals, such as olivinite, etc.
Crystal System: Hexagonal - Dipyramidal
Cleavage: {0001} Indistinct, {1010} Indistinct
Color: White, Yellow, Green, Red, Blue.
Density: 3.16 - 3.22, Average = 3.19
Diaphaneity: Transparent to translucent
Fracture: Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Habit: Colloform - Forming from a gel or colloidal mass.
Habit: Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite).
Habit: Massive - Granular - Common texture observed in granite and other igneous rock. Crystal Habits include the typical hexagonal prism with the hexagonal pyramid or a pinacoid or both as a termination. Also accicular, granular, reniform and massive. A cryptocrystalline variety is called collophane and can make up a rock type called phosphorite and also can replace fossil fragments.
Hardness: 5
Luminescence: Non-fluorescent.
Luster: Vitreous (Glassy)
Streak: White

Associated Minerals are hornblende, micas, nepheline and calcite.
Other Characteristics: An unusual "partially dissolved" look similar to the look of previously sucked on hard candy.

Notable Occurrences include Durango, Mexico; Bancroft, Ontario; Germany and Russia.
Best Field Indicators are crystal habit, color, hardness and look.
Radioactivity: Apatite is Not Radioactive

I apologize, took a little while to post another one, been busy. I hope you are doing good.

Best regards,
Oscar G. Shelly

Saturday, February 28, 2009

Caramel? no, not at all, fire agate, one of many quartz' forms

Fire agate

Probably one the most fascinating mineral combinations there is (according to me), hematite and amorphus silica (quartz). I'd say this is the equivalent to an opal, only the iridiscense is not because of water molecules, but because of the iron oxide embedded in the silica. First time I saw one of these specimens - common in Aguascalientes, Mexico - was in college in my Mineralogy class back in 1975 (Faculty of Engineering of the National Autonomous University of Mexico), and I fell off my chair, I was in shock with the beauty of this baby.

Anyhow, I am not sure why this mineral has never made it to precious stone status, but if I ever become president of the Mexico, I'll declare it the stone of the country. If you don't like it as much as I do, don't vote for me.

Ok, let us see what are the fire agate (another form of quartz) life technical specifications:

Chemical Formula: SiO2
Environment: Sedimentary, metamorphic, and igneous rocks.
Locality: Very common mineral found world wide.
Name Origin: From the German "quarz", of uncertain origin according to many, however I heard once that it comes from the old saxonic that means ice very frozen.

Synonyms of quartz:

Agate - banded variety of chaledony
Amethyst - purple
Avanturine - feebly translucent chalcedony
Carnelian - flesh red chalcedony
Cat's Eye - chatoyant
Chalcedony - microcrystalline quartz
Chert - cryptocrystalline quartz
Chrysoprase - apple green chalcedony
Citrine - yellow
Flint - microcrystalline quartz
Hornstone - flint
Jasper - red or brown chalcedony
Moss Agate - variety of chaledony
Plasma - green chalcedony
Prase - leek green chalcedony
Rock Crystal
Rose Quartz - rose colored
Sapphire Quartz - blue colored
Smoky Quartz - brown to black
Tiger Eye - pseudomorph of asbestos

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).
Habits: Crystalline - Coarse - Occurs as well-formed coarse sized crystals.
Crystalline - Fine - Occurs as well-formed fine sized crystals.
Druse - Crystal growth in a cavity which results in numerous crystal tipped surfaces.
Hardness: 7 - Quartz
Luminescence: Triboluminescent.
Luster: Vitreous (Glassy)
Streak: White

I hope you enjoy a terrific weekend, today is 2/28/09, visit my website if you have some chance: Oscar el Mexicano

Thursday, January 1, 2009

Nominated one of the 100 Best Blogs for Earth Science Scholars

By: by Bachelors Degree Online

Thanks & Happy New Year!

Oscar G. Shelly

Extinct minerals: Brazilianite...due to mineralogists? or Ice....due to global warming?


I read something today (1/1/2009), - Happy New Year by the way - that caught my eye, and it was related to minerals extinction. The article / blog made me wonder if in fact minerals are subject to extinction due to Geological causes, according to Andrew's Geology blog. After serious, and some not so serious thinking, I came up to the following conclusions / examples that I put into consideration for comments / critics.

I believe that is true that some minerals are subject to extinction, due to a variety of causes / phenomena. The first one that comes to mind is the mineral ice. If after all, Al Gore is right with his Global Warming theory, this will be the cause for melting icebergs, glaciers, and the poles in general, which will make ice disappear from the Earth, or better yet: follow one of Newton's laws; thus, ice will be transformed into water and/or vapor. What about snow?

Now, another one that comes to mind is the Brazilianite. A beautiful mineral with a beautiful name too in honor of its country in which it was discovered Brazil. Why does this mineral being so much harder, and stable than ice would disappear from the Earth? well, the disappearance will not be from the Earth, but from the pegmatites of Brazil (at least the ones so far discovered and exploited); Brazilianite specimens have been placed into many Museus and mineralogical collections around the globe, including mine. This is a mineral you don't see anymore in trade shows, so as far as I am concerned, there is another cause for mineral extinction: Avid mineralogists.

Let me take advantage of discussing about this amazing mineral sadly extinct to talk about its mineralogical features as follows:

Chemical Formula: NaAl3(PO4)2(OH)4
Composition: Molecular Weight = 361.91 gm
Sodium 6.35 % Na 8.56 % Na2O
Aluminum 22.37 % Al 42.26 % Al2O3
Phosphorus 17.12 % P 39.22 % P2O5
Hydrogen 1.11 % H 9.96 % H2O
Oxygen 53.05 % O

Name Origin: Named after its first discovery in Brazil.
Crystal System: Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 21/n
Cleavage: [010] Good
Color: Colorless, Greenish yellow, Yellow green, Light yellow.
Density: 2.98
Diaphaniety: Transparent
Fracture: Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Habit: Euhedral Crystals - Occurs as well-formed crystals showing good external form.
Habit: Spherical - Spherical, rounded aggregates.
Hardness: 5.5 - Knife Blade
Luster: Vitreous (Glassy)
Streak: White
Radioactivity: Brazilianite is not Radioactive