Author Archives: NDrockclub

About NDrockclub

Central Dakota Gem & Mineral Society, based out of Bismarck, ND. Local rock club.

Show & Tell

The May 7th program portion of our meeting will include Show & Tell.  Bring your whatsits, your leverites, your FLRs (funny-looking-rocks), or your fancy and fabulous pieces.  With so many brains on hand, we’re sure any questions will be answered!

Also, from 11am-1pm the First Annual Snail Crawl will be held for families of Pebble Pups (members under 18 years of age).  Contact Becky for more information.

campeloma 1

Hematite

[Guest Author Matt Doyle]

Hematite, famous modernly for the steel-grey jewelry often made from it, is more commonly a rust-red ore when found in mining iron[1].  A iron oxide (Fe2O3), hematite’s name comes from haema, the Greek word for blood[2], and most of its direct historical impact comes from that red form.  While hematite is incredibly common – the most common form of iron ore[3] – even in ancient times it was appreciated for itself, and not only for the metal it could produce.  In modern times, magnets are used to harvest hematite from mine tailings.

hematite1     Red hematite most commonly possesses an earthy luster, appearing anywhere from rust-colored to Powdered red hematite is also known as rouge.  Perhaps most famous as a cosmetic used for centuries to redden the skin, it is the same substance as jeweler’s rouge, used to polish metal and gemstones, and also frequently used to help strop a barber’s straight razor.  Red ochre and yellow ochre painting pigments also owe their color to a mixture of red hematite and clay – unhydrated in red ochre, and hydrated in yellow[4].  Maybe most strikingly, hematite is the basis of red chalk, and red chalk drawings have many prominent places in human history and the history of art, including the sketches of Leonardo DaVinci, the body painting of corpses in paleolithic cultures one hundred and sixty to eighty thousand years ago[5], and numerous cave paintings dating back as much as forty thousand years[6].  Red chalk mines dates back as far as 5000 BCE.

Grey hematite, unlike the “bloodstone” variety that gave it its name, has a metallic luster, and can appear almost like a dark mirror when sufficiently polished.  Faceted, it appears nearly black, and smooth, it has a gray, lustrous tone similar to a black pearl.  Used as a gemstone in jewelry, for gilding, or for carved intaglios, it was especially popular in Victorian England, and is still used today, in part because it is common enough to be relatively affordable. In its more jewel-like form, it has been sought after for over two millennia, since the Etruscans found deposits of it on the island of Elba.

hematite2     Outside of iron mines, hematite is commonly found in banded iron formations, hot springs, clay banks, and other places where iron interacts with water[7] (or more rarely, without water, as a result of volcanic activity).  Whether grey or red, it always leaves a red streak[8] (and a grey stone leaving a red streak is often striking and startling to students in the lab seeing it for the first time). Hematite often contains enough inclusions of magnetite to appear attracted to magnets, however, hematite itself is only weakly ferromagnetic when encountered at room temperature.  Its specific magnetic properties are variable in peculiar ways depending on the scale of the hematite crystal, and its small magnetic moment, as well as the temperatures at which it transitions from antiferromagnetic to paramagnetic, have been the subject of much discussion since the 1950s (and as such, could make up an essay – or many scholarly papers – of their own).

[1] https://en.wikipedia.org/wiki/Hematite

[2] http://www.mindat.org/min-1856.html

[3] http://geology.com/minerals/hematite.shtml

[4] http://www.mineralszone.com/minerals/ochre.html

[5] https://en.wikipedia.org/wiki/Pinnacle_Point

[6] http://www.eurekalert.org/pub_releases/2007-10/asu-rfe101207.php

[7] http://mars.nasa.gov/mer/spotlight/hematite01.html

[8] http://www.minerals.net/mineral/hematite.aspx

July 10 Harmon Lake

Come join us on July 10th, 1pm, up at Harmon Lake to learn about Cannonball Concretions.  Follow 1806 north of Mandan, about 11 miles.  Shelter 2.

HarmonLake

Rock Equipment For Sale

14″ rock cutting saw, 1 new blade, extra blade cutting oil
Polisher with stand & water drip pail
8 rock tumblers: 3-30lb capacity
Combination trim saw, grinder & shaper, sander & polisher
A lot of extra parts – some new, some used

New price would be over $5000, but I will sell all of this for $2500.

Contact

Melvin Berg
101 Stewart Ave, Box 736
Underwood, ND 58576

Grit – Treasures of Sea & Earth

Treasures of Sea & Earth supply grit for your rock tumbling needs.  For club discounts, please see the Member page.  For more information, please check out http://treasuresofseaandearth.com/ Currently available:

400                        5lb: $30.00         1lb: $6.00

600                        5lb: $30.00         1lb: $6.00

46/70                    5lb: $18.80        1lb: $4.00

120/220                5lb: $21.00        1lb: $4.20

Tin Oxide             5lb: $145.00     1lb: $29.00

Tripoli Powder   5lb: $18.80         1lb: $4.00

Plastic pellets     1lb: $4.20

Gypsum

The mild-mannered gypsum is not only a pretty sulfate to look at, but is harvested for numerous functions. The crystals are tabular, and often twinned. It can also form massive, granular, and fibrous habits. Radiating forms are called “daisy gypsum,”, and rose-shaped forms “desert rose.” Gypsum tends to be fairly drab with color, varying from near colorless, white, and gray, to a more green, yellow, or reddish hue. Its name comes from the Greek word “gypsos,”, meaning chalk or plaster.

It is mined for use as a fertilizer, plaster, chalk, and sheetrock / gypsum board. The granular form called alabaster is used in carving and sculpture. “Plaster of Paris” is dehydrated gypsum – by adding water back into the powder, the mixture creates an exothermic reaction (gives off heat), and “sets” into a hardened form. This is useful for making casts of objects. The fibrous crystal form is called “satin spar” and “senelite.”

gypsum 3

Selenite – fibrous form

gypsum 4

Alabaster – granular gypsum

gypsum 2

Desert Rose – rosette gypsum

Gypsum has a white streak, but ranges from transparent to opaque. It is a very common mineral found in many locations. It can be deposited from lakes and seawater, hot springs, and other evaporative environments.

**Becky Trivia** Two fossil sites across North Dakota, on opposite ends of the state, hold gypsum. To the east, the Pembina Gorge locality once held a vast inland sea. Gypsum is so plentiful there it is the main mineral replacing the mosasaur and fish fossils, giving them a very soft, fragile form. Just off site, people can wander and pick up satin spar spears ranging from clear to black. To the west, the Whiskey Creek locality was once a swampy environment similar to the everglades. Sheets of gypsum can be found in and around those crocodile fossils as well.

The chemical formula is CaSO4·2H2O, and a hardness of 2 on the Mohs scale.

 

Pellant, Chris. Rocks and Minerals. New York: Dorling Kindersley, 1992. Print. Pg. 110.

http://www.minerals.net/mineral/gypsum.aspx

http://www.mindat.org/min-1784.html

2016 January Program: Gemstone Trees

Hello members!  The program following the club meeting on January 10th will be about making gemstone trees.  You’ve probably seen them around – eBay, Amazon, etsy – they’re all the rage.  Becky will provide take-home printed directions, gemstones (rose quartz, lapis lazuli, amethyst, malachite, and more) and wires enough to build a small tree (like the one above).  She has a limited number of needle-nose pliers however, so if you have some lying around, please bring them too!  Once you have the basics, no doubt your trees will grow and grow.

 

Christmas Party

This is the your reminder for our upcoming Christmas Party.  We are set to have the party at the north A & B Pizza shop at 1:30 pm this coming Sunday, December 6th.

 

The club will buy the pizza and the pop for the attendees.  For members who are of age, stronger drinks are available at your own expense.

 

We will have the gift exchange and according to our discussion at our last meeting, if you wish to participate in the gift exchange, please bring an exchange gift in the $10 neighborhood.  We encourage you to bring, if possible, a gift relative to the rock and mineral hobby.

 

This Christmas party is in lieu of our December meeting.  See you all on Sunday at the North A&B.