Mineral Notes - 2006
MINERALOGY/MICROMOUNT January 14, 2006.
Meeting was called to order by John Good at 7:40 PM, in Kathy Dedina’s absence.
The topic for the Study Group’s case in the March show was discussed. We agreed
on India, since most members have material from India, particularly the Deccan
Traps.
Programs for coming months were planned.
In February we will do Nova Scotia. Assignments were:
Jim Daly- Zeolites
John Good- Geology
Kathy Dedina- Gold
In March we will discuss inclusions in minerals.
This month’s program was a video on salt (Halite) from the History Channel. It
focused on salt mining in Louisiana and in Poland.
We also saw a brief segment of a video on the caves in Sequoia National Park.
Dorothy Auler and John Good provided refreshments.
Submitted by Jim Daly
NOVA SCOTIA ZEOLITES by Jim Daly
February 2006
The cliffs surrounding the Bay of Fundy produce some of the finest zeolites
known. From their first discovery in the 1820’s until the discovery of the
zeolites from the Deccan traps in India in the mid-twentieth century they were
considered the best in the world. They can still be collected today, since more
are continually exposed by erosion caused by the tides. These tides, the highest
in the world, can make collecting hazardous unless you are aware of their
schedule.
The zeolites found are:
Stilbite-Ca- Found as sheafs, fans and bowties. Reddish-orange is the most
common color, although it can range from white to brown. It is the official
mineral of Nova Scotia.
Heulandite-Ca- This is also common, but not nearly as attractive as the Stilbite.
It is most common as an orange or pink druse. It has also been found as
colorless, pearly crystals.
Analcime is found as white to brown crystals.
Chabazite- I have been unable to find out which variety: -Ca, -Na, or –K is
found here. The crystals are simple rhombs, and come in a range of colors:
colorless, white, orange, red, pink or brown. Some of the best chabazite
specimens in the world have come from here. Chabazite is not found in the Deccan
traps.
Gmelinite- is found often as a coating on chabazite, and sometimes as isolated
crystals. It can easily be mistaken for chabazite. Again, I have been unable to
find out if it is the –Ca, -Na, or –K type.
Natrolite- is found as very thin delicate prisms.
Thomsonite-Ca- is considerably less common. It is found as colorless balls.
Mordenite- is quite uncommon, despite this being the type locality for the
mineral, and it’s being named for the town of Morden, Kings Co., NS. It is found
as small massive nodules.
Laumontite, Mesolite and Apophyllite have also been reported.
MINERALOGY/MICROMOUNT March 11, 2006.
Meeting was called to order by Kathy Dedina at 7:35 PM.
Announcements were made regarding upcoming shows: The ESCONI show, March 18 &
19, the Chicagoland show on Memorial Day weekend, and the Clement Mineral Museum
show June 3 & 4, in Marion, KY.
Programs for coming months were planned.
There will be no meeting in April due to a conflict with MAPS.
In May we will do New Zealand. Assignments were:
Jim Daly- Minerals and localities
Sheila Bergmann- Geology
Kathy Dedina- Mining history
In June we will do Tasmania. Assignments were:
Geology- Sheila Bergmann
Mining history- Kathy Dedina
Minerals and localities- Jim Daly
This month’s program was on inclusions in minerals.
John Good discussed inclusions in quartz.
Smoky quartz often has minute cavity inclusions containing carbon dioxide or
water. If there is a sufficient number of these minute fluid inclusions then the
quartz becomes opaque and is called milky quartz. Smoky quartz often has
cavities containing both liquid and gas phases known as two-phase inclusions or
enhydros. In rare cases, two-phase inclusions in quartz can be visible to the
unaided eye and may show actual movement of the gas phase within the liquid
phase.
Many different minerals can form as inclusions within smoky quartz. Some of
these are rutile, tourmaline, chlorite, goethite and hematite.
Phantom quartz shapes are sometimes present in the interior of smoky quartz
crystals, outlining an earlier stage of the crystal’s formation. These phantoms
are usually composed of other minerals such as chlorite or other varieties of
quartz such as milky quartz, colorless rock crystal, or smoky quartz of lighter
or darker shades which form on most or all of the surfaces of the quartz crystal
at a particular point in time during its growth, after which the quartz crystal
resumes its crystallization enclosing the phantom crystal outline within itself.
Water-clear doubly terminated quartz crystals microscopic to 10 centimeters in
length occur in the Cambrian Little Falls Dolomite in Herkimer County, NY. These
are called “Herkimer Diamonds”. Some of these crystals have holes containing
liquid and solid inclusions. Sometimes the holes take the form of negative
crystals. The hole-filling liquids, solids and gases form a “time capsule” of
materials available at the time of crystal formation. The possible depth of the
rocks beneath the surface during crystal formation may be derived from a study
of the liquid inclusions.
There are two types of inclusions found in Herkimer quartz. Primary inclusions
were formed during the initial growth of the crystal. Secondary inclusions were
formed when fluids entered a fracture in a crystal and were trapped there when
the crystal healed over. Healed fractures are found in about 75% of Herkimer
quartz crystals. Some inclusions contain a black hydrocarbon called “anthraxolite”.
It is usually seen as black, dull or shiny fragments or smears within a crystal
or inclusion. The hydrocarbon was derived from the lifeforms living during the
time of the deposition of the sedimentary rocks.
Kathy Dedina discussed inclusions in gemstones. Inclusions in gemstones are
irregularities such as solid minerals or crystals, liquid-filled cavities,
gas-filled cavities, unfilled cavities such as negative crystals, fractures and
irregularities that produce an optical effect. Inclusions may be visible to the
naked eye or need the use of loupes, microscopes or other high tech equipment.
Inclusions can be categorized by the time of formation. Protogenic inclusions
formed before the including gemstone which entraps the material as it grows
around the inclusion. Rubies from Burma are an example. Syngenetic inclusions
form at the same time as the including gemstone. Cavities are formed as parts of
the gemstone grow at different rates eventually enclosing a cavity which may be
filled with solid, liquid or gas or combinations of the three. Epigenetic
inclusions formed after the gemstone finished growth. This may be immediately
after or even millions of years later. As surrounding temperature decreases
material held in a solid solution is forced out and crystallizes. The tiny
oriented needles of rutile in star stones are an example. Secondary cavities
form when fractures in stones are healed. In the process characteristic patterns
of many tiny crystals or negative crystals are formed.
Most inclusions in gemstones are undesirable. They can affect clarity and
increase the risk of breakage. There are some inclusions that increase the value
and beauty of gemstone material. The most common inclusion of value is the
orientation most frequently of rutile to form the star or asterism of ruby,
sapphire, garnet and rose quartz. The minute needles are oriented on three
planes of the gem decreasing the clarity of the stone but producing the highly
desirable 6 sided star. Naturally occurring star rubies and star sapphires rival
the best clear gems in value. Needles oriented in one plane produce the cat’s
eye or chatoyancy in tourmaline, beryl, quartz and andalusite. When the
potassium-rich feldspar orthoclase cools it forces the sodium impurity in its
structure to migrate out and form the sodium-rich feldspar albite in localized
pockets. This combination produces the effect called adularescence as seen in
moonstone. The presence of pyrite in lapis lazuli increases its beauty and
distinguishes it from similar stones such as sodalite. Adventurine is green
quartz colored by tiny flakes of fuchsite mica. Rutile, actinolite, hedenbergite,
hematite, tourmaline, chlorite, cookeite, mica, pyrite, galena, adularia, and
other minerals are included in quartz. The most valuable is rutilated quartz.
Various agates owe their lapidary value to included material Moss agate and
plume agates are good examples.
Most gemstones are negatively affected by inclusions. The dark spots in diamonds
were called carbon spots. Today it is known that carbon or graphite spots in
diamonds are rare. The spots may actually be garnet, zircon, peridot, other
diamonds, pyrite, rutile, silica, bronzite, spinel, serpentine, phlogopite,
olivine, diopside, pyrrhotite, pentlandite, ilmenite, chlorite, calcite,
goethite, biotite, hematite and other iron oxides.
Jim Daly reported on an unusual aspect of liquid inclusions in halite. Since
halite is soluble in the included water, the included bubble can actually move
over a long period of time, particularly if there is a temperature gradient
across the bubble. The liquid in the bubble will dissolve salt from the hotter
side and precipitate it on the cooler side, so that the inclusion slowly
migrates toward the hotter side.
Dorothy Auler and Kathy Dedina provided refreshments.
Submitted by Jim Daly
MINERALOGY/MICROMOUNT May 13, 2006.
Meeting was called to order by Kathy Dedina at 7:30 PM.
Announcements were made regarding upcoming shows: The Chicagoland show on
Memorial Day weekend, and the Clement Mineral Museum show June 3 & 4, in Marion,
KY.
The program for June will be Tasmania. Assignments are:
Geology- Sheila Bergmann
Mining history- Kathy Dedina
Minerals and localities- Jim Daly
This month’s program was on New Zealand.
Sheila Bergmann described the geology of New Zealand.
New Zealand is on the confluence of the Pacific and Australian plates. The North
Isand is on the edge of the Australian plate, and the plate boundary runs
through the middle of South Island. The Pacific plate is subducting under the
Australian plate. As a result, New Zealand is geologically quite active, with
earthquakes, volcanoes, geothermal areas and high mountains. There have been six
major periods in New Zealand’s geologic history:
Deposit of sediments, 545-370 mya.
Tuhua Orogeny, 370-330 mya- uplift to form mountain.
New Zealand Geosyncline, 330-142 mya- accumulation of sediments.
Rangitata Orogeny, 142-99 mya- compression and folding of sediments.
Break-up, 99-24 mya- New Zealand breaks away from Gondwana.
Kaikoura Orogeny, 24 mya- modern- uplifting of the Southern Alps.
Jim Daly spoke about the minerals and mineral localities of New Zealand.
There are 301 New Zealand localities listed on the website mindat.org, and this
list is far from complete. There are 273 valid mineral species listed from these
localities, among which are 12 type localities. Only 20 localities were
discussed due to time limitations.
Kathy Dedina talked about the history of mining in New Zealand.
The first mining was done by the Maori, who first settled the islands about 1000
AD. They mined “greenstone”, nephrite jade. Today mining of “greenstone” can
only be done with permission of the Maori tribal organizations, and no
unpolished material can be exported.
Gold was first discovered at the Coromandel Peninsula of the North Island in
1852, and on the South Island in 1856. The first workings were in alluvial
deposits. Hard rock mining began in the 1860s.
Ironsand is found on the beaches on the west side of both islands. This is
mainly “titanomagnetite”, a titanium-rich magnetite. It is difficult to smelt
conventionally. In 1960, however, the Japanese were looking for a source of this
material, and are now using it in steelmaking.
Several clays, perlite and pumice are found in economic deposits. In addition,
zeolites have been mined at Ngakuru since 1993.
New Zealand is exploring the development of off-shore deposits of copper, zinc
and gold associated with sulfides at active undersea volcanoes. They have until
August 2006 to claim these areas. Estimates of the seafloor deposits are up to
$500 billion, but extraction costs, which are still unknown, may easily outweigh
the value.
John Good provided refreshments.
Submitted by Jim Daly
MINERALOGY/MICROMOUNT June 10, 2006.
Meeting was called to order by Kathy Dedina at 7:30 PM.
The program for September will be a video.
This month’s program was on Tasmania.
Sheila Bergmann’s presentation on the geology of Tasmania was read by Kathy Dedina.
It was difficult to find a geological map of Tasmania, or much information on the geology of the central and eastern parts of the island.
Western Tasmania is mainly composed of late Pre-Cambrian rocks, with zones of early Devonian between. There are also Cambrian volcanics intruding the Pre-Cambrian. These are the areas with the most mineralization.
Eastern Tasmania is characterized by extensive emplacements of Jurassic dolerites. This did not affect the western part of the island.
Kathy Dedina talked about the history of mining in Tasmania.
The first exploration for mineral resources was in the late 1850’s, in an effort to stop the exodus of residents to the goldfields of New South Wales. Nothing significant was found at that time.
The first significant discovery was in 1871 of a tin deposit. This developed into the Mt. Bischoff tin mine in Waratah, which in the 1880’s was the richest tin mine in the world. This was followed by the discovery of gold and osmiridium in the Pieman tributaries in 1879, silver and lead in the Zehann-Dundas area in 1882, and copper at Mt. Lyell in 1883.
At this time it is estimated that presently known resources will be exhausted within 15 years. Location and development of new mines is hampered by restrictive environmental and mining laws. 30% of the land area is off limits to mining due to environmental protection, and another 10% because of other laws restricting mining. Gold mining in particular is almost impossible because of laws restricting the disposal of the cyanide used in the recovery process.
Jim Daly described the minerals and collecting localities of Tasmania.
Tasmania, although a relatively small island, has a wealth of mineral collecting opportunities. Mindat lists 324 species, for which Tasmania is the type locality of 9, and 128 localities overall. This is in area perhaps one quarter of the state of Ohio!
Aside from the occurrences of jasper, chalcedony, petrified wood, etc., there are four main areas of interest:
The nickel mines in the west, near Heazlewood. Of these, the Lord Brassey Mine is probably the most interesting. It is the type locality for Heazlewoodite and Hellyerite, and has produced 23 different minerals, many of which are rare.
The famous crocoite locality near Dundas. This was a lead mining region. There are 14 mines in the area. Of these, the Platt Mine is being worked commercially for specimens, and the Magnet Mine, or at least it’s dump, is available for collecting. While whenever crocoite is mentioned, this area is the first (and perhaps only) locality that comes to mind, it is not the type locality. That is in Russia.
The area around Launceston in the northern part of the island, and the islands off the north coast. These areas are noted for zeolites, such as chabazite, phillipsite, thomsonite, analcime, gmelinite, gonnardite, gyrolite, harmotome, heulandite, levyne, scolecite, stellerite, stilbite, mesolite, mordenite, natrolite, etc.
The Kara Mine near Hampshire, in the northeast part of the island. This was a tungsten mine. The main ore was scheelite. In all 50 species have been found there. It is especially noted for good andradite crystals. A book was recently written about the mine by Steve Sorrell and Ralph Bottrill.
The state government of Tasmania takes a very enlightened approach to collectors. Mineral Resources Tasmania, (www.mrt.tas.gov.au/), the equivalent to our state geologic surveys, has set aside 10 areas where “fossicking”, as collecting is known there, is permitted and even encouraged, on state lands. Their website has maps to these areas and lists of minerals found there. The areas include the Lord Brassey Mine, the Magnet Mine, a quarry with zeolites, and a number of sites for lapidary materials.
Collectors in Tasmania must be generally better behaved than here. The pages for some of these sites state that historical mining artifacts are on these properties, and simply asks collectors to please not disturb them. Can you imagine that to be effective here?
John Good provided refreshments.
Submitted by Jim Daly
Last Updated 12/05/2007
Number Of Visitors Since 2/2/2006