The Del Air Rockhounds Club Welcomes You!!

The Del Air Rockhounds Club was founded in 1952 with members mostly residing in the San Fernando Valley area of California. Our club is a non-profit organization dedicated to sharing knowledge of the lapidary arts and techniques, geology, mineralogy and related fields. We own our own lapidary equipment with members available to teach and demonstrate lapidary techniques to other members. Our members enjoy lapidary related programs, demonstrations, exhibitions, displays and lectures. We also take monthly field trips to our local deserts & mountains for exploration and the study and collection of lapidary and mineral specimens.

BIG NEWS!!!! BIG NEWS!!!! BIG NEWS!!!! BIG NEWS!!!!

THE DEL AIR ROCKHOUNDS

GEMBOREE SHOW IS COMING!!

Del Air Gemboree Show February 24th and 25th 2012

The Del-Air Rockhounds invite you to join us for our annual GEMboree Show on Friday February 24th 2012 from 3-9 pm
and Saturday February 25th 2012 from 10 am-5 pm.

Admission and parking is free!

Please right click on the flyer to the left to open it in a new window. From this new window you will be able to print the flyer.

Write your name, address and phone # on the back and bring it with you to the show to be entered into a special web-only drawing for a spectacular door prize. Winners need not be present to win.

FIND UNIQUE GIFTS - CRYSTALS – FOSSILS – GEMS – BEADS

YOUTH GAMES – PRECIOUS STONES – DISPLAYS

SPHERES – MINERAL SPECIMENS – HANDMADE JEWELRY

See you all at the show!!

Del Air Gemboree Gem and Mineral Show Wants YOU!!

The 2012 Del Air Gemboree Gem and Mineral Show

Wants YOU!!

to come and have a great time!

Friday February 24th and Saturday the 25th



Print this jpeg flyer and bring it to the show
for a special drawing!!

Or Click HERE for a .pdf!

February 2012 Rock of the Month

Gneiss

Gneiss is a typical rock type formed by regional metamorphism, in which a sedimentary or igneous rock has been deeply buried and subjected to high temperatures and pressures. Nearly all traces of the original structures (including fossils) and fabric (such as layering and ripple marks) are wiped out as the minerals migrate and recrystallize. The streaks are composed of minerals, like hornblende, that do not occur in sedimentary rocks. In gneiss, less than 50 percent of the minerals are aligned in thin, foliated layers. You can see that unlike schist, which is more strongly aligned, gneiss doesn't fracture along the planes of the mineral streaks. Thicker veins of large-grained minerals form in it, unlike the more evenly layered appearance of schist. With still more metamorphism, gneisses can turn to migmatite and then totally recrystallize into granite. Despite its highly altered nature, gneiss can preserve geochemical evidence of its history, especially in minerals like zircon which resist metamorphism. The oldest crustal rocks known are gneisses from western Greenland. Their carbon isotopes show that life existed there at that time, nearly four billion years ago. Gneiss makes up the largest part of the Earth's lower crust. Pretty much everywhere on the continents, you can drill straight down and eventually strike gneiss. Gneiss is an old German word meaning bright or sparkling.

January 2012 Rock of the Month

Granite

Granite is the signature rock of the continents. More than that, granite is the signature rock of the planet Earth itself. The other rocky planets—Mercury, Venus and Mars—are covered with basalt, as is the ocean floor on Earth. But only Earth has this beautiful and interesting rock type in abundance. Three things distinguish granite. First, granite is made of large mineral grains (which is where its name came from) that fit tightly together. Second, granite always consists of the minerals quartz and feldspar, with or without a wide variety of other accessory minerals. The quartz and feldspar generally give granite a light color, ranging from pinkish to white. But that light background color is punctuated by the darker accessory minerals. Thus classic granite has a "salt-and-pepper" look. The most common accessory minerals are the black mica biotite and the black amphibole hornblende. Third, almost all granite is igneous, meaning it solidified from a fluid state and almost all granite is plutonic, meaning it did so in a large, deeply buried body or pluton. The random arrangement of grains in granite is evidence of its plutonic origin. Granite is found in large plutons on the continents, in areas where the Earth's crust has been deeply eroded. This makes sense, because granite must solidify very slowly at deeply buried locations to make such large mineral grains. Plutons smaller than 100 square kilometers are called stocks, and larger ones are called batholiths. On the grandest scale, granite represents the way the continents maintain themselves. The minerals in granitic rocks break down into clay and sand and are carried to the sea. Plate tectonics returns these materials through seafloor spreading and subduction, sweeping them beneath the edges of the continents. There they are rendered back into feldspar and quartz, ready to rise again when and where the conditions are right.