generally meets the third Wednesday of each month, August through May.
We now meet in Penn State's Earth and Engineering Sciences Building, on White Course Drive off North Atherton Street.
See driving directions and campus maps.
All are welcome to attend our meetings!
Parents must provide supervision of minors.
Mineral collectors and rockhounds, earth scientists and dinosaur lovers will all enjoy our activities.
Thank you to all who volunteered, and to all students and parents who attended!
Sorry, we do not have any monthly Junior Rockhounds meetings scheduled at this time.
May 21st regular meeting:
6:30 to 7:30 p.m.: Social hour, refreshments in the lobby
7:30 to 8:00 p.m.: announcements, questions, answers; door prize drawings
about 8:00 p.m.: featured program
The event has free admission, free parking, free door prize drawings and free refreshments, and is open to all (parents/guardians must provide supervision of minors). Bring your friends and share an interesting evening. - - Editor
Chert is a state of matter of silica-rich material that includes crystalline (macro-, micro- and crypto-crystalline) varieties of quartz as well as amorphous and hydrated gels of opaline silica. The states represent a progression of changes (dehydration and increasing crystallinity) referred to as diagenesis (increasing age and metamorphism); hence the plethora of names for a material linked by density, rigidity, hardness and Hertzian fracture properties. If the impact point is close to a free surface, the proximal Hertzian cone is bulbous (bulb of percussion) that spreads radially outwards into an essentially planar fracture surface with smooth concentric ribs as the impact energy dissipates distally. Overlapping Hertzian fracture cones generated from adjacent impact points close to a free surface can produce "flakes" with sharp edges or points that were important to Stone-age cultures. High surface energy associated with crystallites can be released as a glow upon impact.
A use-based nomenclature is difficult to reconcile in the mineral world. If classified by origin and setting, then C-cherts represent precipitates from sea water, F-cherts the precipitates in fractures from silica-rich fluids, and S-cherts are the replacements of pre-existing rocks by pore fluids. Critical factors are the solubility of silica, alumina and iron in the weathering cycle, a porous medium for silica-rich fluids to migrate to an environment with a paucity of clay particles, low temperature, pressure and pH and/or a high partial pressure of CO2 in a turbulent free setting. The volumetrically dominant deposits are the Bedded Cherts that form from diagenetic dissolution and reprecipitation in turbidites and graywacke assemblages, and deep water oozes.
Older rocks harbor the more stable phases, with a restriction of the Banded Iron Formation of the Archean and Proterozoic. The nodular and bedded cherts in shallow marine carbonate assemblages tend to be confined to Paleozoic and Mesozoic age strata: the nodular and bedded chert in North America is hosted in the Middle Ordovician and Devonian carbonate formations, while the widespread flint deposits of Europe occur in the Upper Cretaceous chalks deposits. Agates occur mainly in geodes (gas bubble filling) in lavas. Metastable silica deposits occur only in post-Early Cretaceous strata, with opaline silica occuring mainly in vein and vugs in in post Miocene strata.
The bedded and nodular cherty deposits in Central Pennsylvania occur mainly in the dolomitic strata of the Gatesburg, Mines, Nittany, Axemann and Bellefonte formations of Cambrian and Ordovician age, and the Keyser and Old Port formations of Lower Devonian age. The brown jasper from a site south of Roaring Spring represents a local residual deposit of probable Eocene age.
The many varieties and stages of chert and their close geochemical affinity to host rock can be exploited to match "chert" artifacts to source areas by relatively inexpensive petrographic techniques (thin sections and a polarizing microscope), especially if trace element concentrations are available.
For more current news, see our NMS Bulletin (link at top of sidebar at left).
DRIVING DIRECTIONS and PARKING for Earth & Engineering Sciences Building meetings on the Penn State campus (NOT Minerals Junior Ed. Day): After 5:00 p.m. and on weekends, free parking is available immediately across the street from the building. From North Atherton St. (Business Rt. 322) between College Avenue and Park Avenue, turn west (toward the golf course) off North Atherton at the traffic signal marked "White Course Drive." Go past the parking attendant's booth, follow the curve to the left, then turn right into the parking lot. The building entrance is a little beyond the center of the lot, at the two round concrete planters. Enter the building, then go all the way across the lobby for our social hour & meeting room. We have a simple map at http://www.nittanymineral.org/EESBmap.jpg. For official campus maps see http://www.campusmaps.psu.edu/ .
NMS now has T-shirts in two new colors.
A station at our Minerals Junior Education Day
CELESTINE is under consideration for Pennsylvania State Mineral
Collecting crystals in a quarry
We have 2013 (and other) posters for sale!