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Eric Diaz's Photo Gallery

KQ4-9GHCalcite, Calcite (Var: Iceland Spar)

Santa Rita Mine, El Oro de Hidalgo, Mun. del Oro, Mexico, Mexico

Dimensions: 47 mm x 36 mm x 18 mm

47mm x 36mm x 18mm

Carbonate

(Var. Iceland Spar)

Color and luster: White, colorless, pale shades of gray, yellow, red, green, blue, brown to black when impure; vitreous, dull; streak white.

Hardness: 3

Cleavage: Perfect in three directions, forming a rhombohedron.

Other data: Specific gravity 2.7; ...
Photo ID: 254290     Uploaded by: Eric Diaz   View Count: 449   Approval status: Public galleries    Type: Photo - 768 x 300 pixels (0.2 Mpix)

WCH-84KQuartz, Quartz (Var: Amethyst)

Anahi Mine, La Gaiba mining district, Sandoval Province, Santa Cruz, Bolivia

Dimensions: 1.75 inches x 1.4375 inches x 1.625 inches

1.75" x 1.4375" x 1.625"

This is a specimen of etched amethyst quartz from Anahi Mine in Bolivia. The feeder veins are 12 to 20 inches wide, but vugs can reach 30 x 60 feet! Some of the vugs collapsed, and solutions entered that etched the quartz into almost unrecognizable shapes, like the one above. In other vugs, the crystals are pristine.
Copyright: © 2008 Eric F. Diaz      Photo ID: 241297     Uploaded by: Eric Diaz   View Count: 462   Approval status: Public galleries    Type: Photo - 2304 x 1536 pixels (3.5 Mpix)

YPR-H9Q

U.S. Virgin Islands, USA

3.8cm x 4.2 cm x 3.6 cm

Found on a beach, this vesicular form of the extrusive igneous rock, rhyolite is the product of a composite volcano, which are only found above subduction zones at convergent plate boundaries. Pumice, because of all the gas bubbles trapped within it, is less dense than water and therefore floats on water. Because the magma, which crystallizes into pumice after it has been extruded from a volcano, is so viscous the gas bubbles within it cannot escape easily and thus become trapped once the lava solidifies.

Rhyolite is the extrusive (volcanic) form of the intrusive (plutonic) igneous rock, granite. They both have the same mineral composition--mostly quartz and feldspar. Only the rock texture of each is different. Granite, because it has had time to cool and crystallize slowly underground, has a phaneritic texture with crystals easily visible to the unaided eye. Whereas rhyolite, having been extruded from a volcano and exposed to the cooler air, has crystallized more rapidly thus forming much smaller crystals which are mostly invisible to the unaided eye. This type of a texture is what we call, aphanitic. That's basically the only difference between rhyolite and granite.
Copyright: © 2008 Eric F. Diaz      Photo ID: 218592     Uploaded by: Eric Diaz   View Count: 676   Approval status: Public galleries    Type: Photo - 576 x 384 pixels (0.2 Mpix)

39J-W50Sodalite

Hiassu farm, Itaju do Colônia, Bahia, Brazil

Dimensions: 18 cm x 8.4 cm x 4.2 cm

18cm x 8.4cm x 4.2cm

Tectosilicate

Color and luster: Blue, gray, white, colorless, green; vitreous, greasy; streak white.

Hardness: 5.5-6

Cleavage: Poor, six directions.

Other data: Specific gravity 2.2-2.3; fracture uneven to conchoidal; transparent to translucent; fluorescent; brittle.

Crystals: Isometric; crystals rare; usually dodecahedrons; also compact, disseminated grains, nodular.
Copyright: © 2008 Eric F. Diaz      Photo ID: 218588     Uploaded by: Eric Diaz   View Count: 535   Approval status: Public galleries    Type: Photo - 581 x 768 pixels (0.4 Mpix)
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