The world did not end, which raises the question: should we sue the advertiser that predicted the Rapture / end-of-the-world for false advertising?
Monday, May 23, 2011
Monday, May 2, 2011
Humans from Monkeys?
I refer to your older article on the Waterberg and human evolution. Do you honestly believe humans come from monkeys? Johan, Pretoria Gem and Mineral Club
Hi Johan,
Well, no. We did not evolve from monkeys. Monkeys are our evolutionary cousins, so to speak. A common ancestor of all humans, apes and monkeys existed around 12 million years ago. This common ancestor gave rise to the Asian apes and the African apes. These species developed along their separate ways. About 6 million years ago, in Africa, what are known as the bipedal woodland apes – species such as the Australopithecines and our Homo Sapiens lineage evolved. Then at about 2.5 million years ago, also in Africa, the chimpanzee and the bonobo became separate lineages. I am certainly no expert on this subject and I would refer you to the literature available on the subject for more detail and accuracy that I can provide.
Hi Johan,
Well, no. We did not evolve from monkeys. Monkeys are our evolutionary cousins, so to speak. A common ancestor of all humans, apes and monkeys existed around 12 million years ago. This common ancestor gave rise to the Asian apes and the African apes. These species developed along their separate ways. About 6 million years ago, in Africa, what are known as the bipedal woodland apes – species such as the Australopithecines and our Homo Sapiens lineage evolved. Then at about 2.5 million years ago, also in Africa, the chimpanzee and the bonobo became separate lineages. I am certainly no expert on this subject and I would refer you to the literature available on the subject for more detail and accuracy that I can provide.
Saturday, April 9, 2011
The Universe – Cause and Effect
The Universe is an unimaginably massive and complex system. Everything we know about the Universe points to it operating by absolute physical laws of cause and effect. The Universe, however, does not look like one in which an independent outside agent is intervening, nor is it a Universe in which miracles happen and physical laws are violated by an entity that is above these laws. The application of Occam's razor deletes the hypothesis of a supernatural origin of the universe. And every attempt to demonstrate the existence of any supernatural force affecting the universe fails through rigorous scientific examination. Cosmology provides explanations for how, out of a singularity and subsequent explosive expansion 13.7 billion years ago, the universe came into being.
Sunday, April 3, 2011
Rock of Ages
A sample of the Acasta Gneiss. The Acasta Gneiss is dated at 4.2 billion years old. Specimen size: 5 cm. Specimen and picture: A. Fraser
It is generally accepted that the age of the Earth and the rest of the solar system is about 4.55 billion years (plus or minus about 1%). This value is derived from several different lines of evidence. Unfortunately, the age of the Earth cannot be determined directly from material that is solely from the Earth. Meteorites have been used to date the age of the Earth as these and the other planets were formed at the same time. The Earth is a dynamic planet and the processes of erosion and crustal recycling as a result of plate tectonics have destroyed the entire earliest surface of the Earth. The oldest known exposed rock outcrop found so far is that of the Acasta Gneiss in Canada. The Acasta Gneiss was dated by radiometric means at 4.2 billion years (4.2 Ga) in age (Tsuyoshi, 2007). And, I have a specimen of the Acasta gneiss!
Sunday, March 13, 2011
Science Illiteracy – it’s just depressing
Scientific illiteracy is depressing. It is one of the reasons that creationism, intelligent design (ID) and a plethora of pseudoscience are accepted by so many. It seems that scientific illiteracy and the mistrust of science is on the rise. The media is replete with discussions of intelligent design (IDiocy) and climate change denial ostriches. Many people nowadays cannot address even the simplest scientific question.
How many adults understand what molecules are, and how many can identify DNA as a key to heredity or that the Earth is 4.56 billion years old and not 6000 years old. The lack of a basic understanding of how the earth works is also obvious whenever large earthquakes such as the occurrence 9.0 magnitude quake in Japan last week is covered in the news. The news anchors always ask the same dumb questions of geophysicists ….. how do earthquakes occur, are they on the rise and can we predict them? I am willing to bet that there are still people that believe that the Sun revolves around the Earth! No wonder people confuse scientific research with obsolete religious dogma or far-rightwing political discussions.
How many adults understand what molecules are, and how many can identify DNA as a key to heredity or that the Earth is 4.56 billion years old and not 6000 years old. The lack of a basic understanding of how the earth works is also obvious whenever large earthquakes such as the occurrence 9.0 magnitude quake in Japan last week is covered in the news. The news anchors always ask the same dumb questions of geophysicists ….. how do earthquakes occur, are they on the rise and can we predict them? I am willing to bet that there are still people that believe that the Sun revolves around the Earth! No wonder people confuse scientific research with obsolete religious dogma or far-rightwing political discussions.
Friday, February 18, 2011
Your Mineral Specimen has been Impounded!
As a collector of mineral specimens I often purchase specimens over the Internet. I frequently buy from mineral dealers that specialise in minerals from Peru as I have an interest in minerals from that country. In April 2008 I ordered a mineral specimen from a dealer in Arizona who happened to have a few really neat Peruvian pieces for sale on his web site. After some negotiating of the price I purchased a specimen of aesthetic crystals of siderite, tetrahedrite, chalcopyrite and arsenopyrite. The dealer told me that he had purchased the specimen from a Peruvian dealer at the 1989 Denver Show and that the specimen was from the famous Pasto Bueno mining district. I asked the dealer to ship to specimen to me in South Africa and I further advised him to send it insured with some form of tracking number. With a tracking number one can monitor the progress of the parcel as soon as it comes into South Africa and this is done by simply logging onto the local postal services web page. Directly after my purchase I was advised by the dealer that the specimen had been shipped. I enquired as to whether the parcel had been insured and if he could give me the tracking number. After a week went by he responded to say that he could not insure the specimen and that he has no tracking number for it, but he confirmed that he had indeed mailed it to me. I was concerned with this as it made the parcel vulnerable to theft or simply getting lost in the postal system. A month later the parcel had still not arrived, but I had in the past waited for up to 3 months for a parcel to arrive from Peru so I was not too concerned at this point. I became very concerned when the parcel had not arrived at the end of June. I contacted the supplier again and he suggested that we wait a few more weeks for its arrival. He assured me that if I did not receive it he would refund me in full. Around that time I had read of the theft of mail by local postal workers and how it was on the increase. I imagined the worst - my parcel being stolen by a postal worker who had considered it worthwhile to steal due to its higher than usual weight. I further went on to imagine that the thief had opened the parcel, found what appeared to him to be a worthless rock and had thrown it by the side of a road. It seemed so tragic an event that this specimen may have ended up this way if one considers its formation, geological history and uniqueness. The various carbonate and sulphide minerals would have crystallised in a large rock cavity around 25 million years ago, precipitating from cooling hydrothermal fluids and changes in pH deep within the tectonically active Peruvian Andes. In 1989 mining activity would expose the pocket allowing the light from a Peruvian miner's headlamp to penetrate the darkness onto masses of golden glistening chalcopyrite, quartz and black lustrous sulphide minerals. The miner would have painstakingly removed as many specimens as he could before further mining activity would send them to the crusher. He knew the value of these specimens and taking care that they were not damaged during their removal would mean he could sell them for a few more dollars to supplement his meager pay. One of the specimens he removed was sold to a dealer at the Denver Show in 1989 who placed a picture of it on his mineral web site, which turned out to be the specimen I purchased.
In the middle of September I still had not received the parcel and had not been refunded by the dealer. In late September I received a letter from the customs office at OR Tambo International Airport. The letter stated that an overseas parcel of mine had been impounded as the contents contained iridium and other precious metals. I was astounded! Iridium* is one of the rarest elements on earth and customs had apparently found enough of it in the mineral specimen to impound it! I was told by customs that the parcel had been opened and since the content was not something they recognised, they contacted the South African Diamonds and Precious Metals Regulator (SADPMR) to inspect the specimen. The specimen was analysed by an inspector from SADPMR using a hand-held Energy Dispersive X-Ray Fluorescence spectrometer (EDXRF), which according to the inspector had “detected” appreciable amounts of iridium in the specimen. On that basis the SADPMR advised customs to impound the specimen and have me apply for a license to be in the possession of “unprocessed precious metals”. I was further told by the DPMR that if I disputed their findings the DPMR would have the specimen analysed at Mintek at my cost. I called the inspector at the DPMR that had done the analysis and he very proudly confirmed that he had found iridium in the mineral specimen. As an analytical chemist I have built a career on analysis of materials and I know only too well the pitfalls that accompany chemical analysis, especially where trace element analysis is concerned. I argued with him that a hand-held XRF ('ray' – guns, as I later started calling them) with which he performed the analysis would not provide enough sensitivity or optical resolution to detect iridium at low concentrations. Even detection of an element with such an apparatus does not guarantee a quantitative result. The mineral specimen would also contain large amounts of the elements, iron, copper, carbon, arsenic and other metals and these would all contribute to what analytical chemists call “matrix effects”. These matrix effects would completely mask the presence of all trace elements and give a false positive result for iridium. The analysis of iridium in a complex matrix such as this mineral specimen would be at best a challenge even for large Wavelength Dispersive XRF instruments that have higher sensitivity and resolution and are designed for low-level elemental concentrations. With this in mind I threw a barrage of questions at the inspector about the integrity of the analysis and how could he be sure that iridium had been found. He could not answer any of the questions with confidence and he had not even the slightest idea of what I was asking when I asked him to quote the detection limit of iridium for the hand-held XRF he used for the analysis. The detection limit being the lowest quantity of a substance (in this case iridium) that can be distinguished from the absence of that substance within a stated confidence limit. Every analyst doing trace element should at least understand this and be able to quote the detection limits for the analytical instrument they are using. A hand-held XRF would be effective for say, determining whether confiscated metal bars or ingots were made of pure cast iron or pure iridium. In this case the concentrations of the metals making up these materials are in the very high per cent levels and in this sort of application the hand-held XRF can be effective and I can see why Customs make use of them. However to use an instrument of such limited analytical capability in an attempt to detect trace elements and then still base their decisions on whether to impound a specimen or not on their sketchy results is ludicrous! The analysis report of the DPMR (see below) concludes that the specimen contains 3.45% iridium, 0.49% rhodium, 0.37% gold, 0.31% palladium and 0.13% of ruthenium! The iridium concentration they report is therefore more than 8 million times higher than iridium levels found in the Bushveld Complex! One can make the same conclusions of the other precious metals. After 3 months of receiving the notification that the specimen was to be impounded and after having to provide an affidavit that I would only use the specimen for “display” purposes I was issued with a letter (see below) allowing me to be in the possession of the specimen. From the time of placing the order with the buyer to claiming the specimen took a period of 7 months. The letter concludes that “the amount of precious metals in the specimen would make the extraction non-viable”. Gee, at the levels of precious metals they found I should give up mineral collecting and head for Pasto Bueno in Peru and start mining the richest precious metals deposit on the planet!
The mineral specimen impounded by SA Customs for having 3.45% Iridium and other precious metals
*Additional information on Iridium:
How abundant is the element iridium on Earth? Iridium is a "platinum-group" metallic element that is very rare in the earth's crust. The platinum-group metals include platinum, iridium, palladium, rhodium, ruthenium, and osmium. In the Periodic Table of the Elements, these metals are also in the same columns as the Group 8 elements, which include iron, nickel, and cobalt. Group 8 elements all have a natural chemical affinity for each other, and therefore they tend to collect together in nature. The greatest concentration of iron on Earth is at its core. This is also where the greatest concentration of our planet's iridium resides. When our planet was still forming iridium and iron formed an alloy and sank into the interior of the planet forming its core. At the surface of the Earth, there are only a few environments that contain more than a trace of iridium. Volcanic and plutonic rocks that are rich in iron minerals, such as peridotite, some basalts, and some gabbros, occasionally contain enough platinum-group metals to be profitable to mine. However, these ores are rare. The Bushveld complex in South Africa is one of these rare orebodies that is host to relatively high precious metal concentrations and even then these are at the parts per billion level. In a typical analysis of the Bushveld Complex rocks bearing iridium, this element is only at an average of around 4 parts per billion or 0.0000004%. Iridium is even rarer in sedimentary rocks - in a randomly selected rock weighing one gram, the amount of iridium contained within it would be less than 1 billionths of a gram (1 nano gram). In fact, the amount of iridium is often so low that it sometimes cannot be measured at all using today's scientific equipment without making use of special pre-concentration techniques.
References:
1. Robin, E., L. Froget, C. Jehanno, and R. Rocchia. 1993. Evidence for a K/T impact in the Pacific Ocean. Nature 363:615-617
2. Alvarez, L.W., W. Alvarez, F. Asaro, and H.V. Michel. 1980. Extraterrestrial cause for the Cretaceous-Tertiary boundary extinction. Science 208:1095-1108.
3. Kerr, R.A. 1996. A piece of the dinosaur killer found? Science 271:1806.
4. Kyte, F.T. 1998. A meteorite from the Cretaceous/Tertiary boundary. Nature 396: 237-239.
5.Email correspondence with Prof. Bruce Cairncross and Bushveld PGM concentrations.
6.Michael J. Benton. When Life Nearly Died – The Greatest Mass Extinction of all Time
In the middle of September I still had not received the parcel and had not been refunded by the dealer. In late September I received a letter from the customs office at OR Tambo International Airport. The letter stated that an overseas parcel of mine had been impounded as the contents contained iridium and other precious metals. I was astounded! Iridium* is one of the rarest elements on earth and customs had apparently found enough of it in the mineral specimen to impound it! I was told by customs that the parcel had been opened and since the content was not something they recognised, they contacted the South African Diamonds and Precious Metals Regulator (SADPMR) to inspect the specimen. The specimen was analysed by an inspector from SADPMR using a hand-held Energy Dispersive X-Ray Fluorescence spectrometer (EDXRF), which according to the inspector had “detected” appreciable amounts of iridium in the specimen. On that basis the SADPMR advised customs to impound the specimen and have me apply for a license to be in the possession of “unprocessed precious metals”. I was further told by the DPMR that if I disputed their findings the DPMR would have the specimen analysed at Mintek at my cost. I called the inspector at the DPMR that had done the analysis and he very proudly confirmed that he had found iridium in the mineral specimen. As an analytical chemist I have built a career on analysis of materials and I know only too well the pitfalls that accompany chemical analysis, especially where trace element analysis is concerned. I argued with him that a hand-held XRF ('ray' – guns, as I later started calling them) with which he performed the analysis would not provide enough sensitivity or optical resolution to detect iridium at low concentrations. Even detection of an element with such an apparatus does not guarantee a quantitative result. The mineral specimen would also contain large amounts of the elements, iron, copper, carbon, arsenic and other metals and these would all contribute to what analytical chemists call “matrix effects”. These matrix effects would completely mask the presence of all trace elements and give a false positive result for iridium. The analysis of iridium in a complex matrix such as this mineral specimen would be at best a challenge even for large Wavelength Dispersive XRF instruments that have higher sensitivity and resolution and are designed for low-level elemental concentrations. With this in mind I threw a barrage of questions at the inspector about the integrity of the analysis and how could he be sure that iridium had been found. He could not answer any of the questions with confidence and he had not even the slightest idea of what I was asking when I asked him to quote the detection limit of iridium for the hand-held XRF he used for the analysis. The detection limit being the lowest quantity of a substance (in this case iridium) that can be distinguished from the absence of that substance within a stated confidence limit. Every analyst doing trace element should at least understand this and be able to quote the detection limits for the analytical instrument they are using. A hand-held XRF would be effective for say, determining whether confiscated metal bars or ingots were made of pure cast iron or pure iridium. In this case the concentrations of the metals making up these materials are in the very high per cent levels and in this sort of application the hand-held XRF can be effective and I can see why Customs make use of them. However to use an instrument of such limited analytical capability in an attempt to detect trace elements and then still base their decisions on whether to impound a specimen or not on their sketchy results is ludicrous! The analysis report of the DPMR (see below) concludes that the specimen contains 3.45% iridium, 0.49% rhodium, 0.37% gold, 0.31% palladium and 0.13% of ruthenium! The iridium concentration they report is therefore more than 8 million times higher than iridium levels found in the Bushveld Complex! One can make the same conclusions of the other precious metals. After 3 months of receiving the notification that the specimen was to be impounded and after having to provide an affidavit that I would only use the specimen for “display” purposes I was issued with a letter (see below) allowing me to be in the possession of the specimen. From the time of placing the order with the buyer to claiming the specimen took a period of 7 months. The letter concludes that “the amount of precious metals in the specimen would make the extraction non-viable”. Gee, at the levels of precious metals they found I should give up mineral collecting and head for Pasto Bueno in Peru and start mining the richest precious metals deposit on the planet!
The mineral specimen impounded by SA Customs for having 3.45% Iridium and other precious metals
*Additional information on Iridium:
How abundant is the element iridium on Earth? Iridium is a "platinum-group" metallic element that is very rare in the earth's crust. The platinum-group metals include platinum, iridium, palladium, rhodium, ruthenium, and osmium. In the Periodic Table of the Elements, these metals are also in the same columns as the Group 8 elements, which include iron, nickel, and cobalt. Group 8 elements all have a natural chemical affinity for each other, and therefore they tend to collect together in nature. The greatest concentration of iron on Earth is at its core. This is also where the greatest concentration of our planet's iridium resides. When our planet was still forming iridium and iron formed an alloy and sank into the interior of the planet forming its core. At the surface of the Earth, there are only a few environments that contain more than a trace of iridium. Volcanic and plutonic rocks that are rich in iron minerals, such as peridotite, some basalts, and some gabbros, occasionally contain enough platinum-group metals to be profitable to mine. However, these ores are rare. The Bushveld complex in South Africa is one of these rare orebodies that is host to relatively high precious metal concentrations and even then these are at the parts per billion level. In a typical analysis of the Bushveld Complex rocks bearing iridium, this element is only at an average of around 4 parts per billion or 0.0000004%. Iridium is even rarer in sedimentary rocks - in a randomly selected rock weighing one gram, the amount of iridium contained within it would be less than 1 billionths of a gram (1 nano gram). In fact, the amount of iridium is often so low that it sometimes cannot be measured at all using today's scientific equipment without making use of special pre-concentration techniques.
References:
1. Robin, E., L. Froget, C. Jehanno, and R. Rocchia. 1993. Evidence for a K/T impact in the Pacific Ocean. Nature 363:615-617
2. Alvarez, L.W., W. Alvarez, F. Asaro, and H.V. Michel. 1980. Extraterrestrial cause for the Cretaceous-Tertiary boundary extinction. Science 208:1095-1108.
3. Kerr, R.A. 1996. A piece of the dinosaur killer found? Science 271:1806.
4. Kyte, F.T. 1998. A meteorite from the Cretaceous/Tertiary boundary. Nature 396: 237-239.
5.Email correspondence with Prof. Bruce Cairncross and Bushveld PGM concentrations.
6.Michael J. Benton. When Life Nearly Died – The Greatest Mass Extinction of all Time
Wednesday, January 5, 2011
Crystal Healing, Pink Unicorns and the Tooth Fairy
How serious do we take the claims of ‘crystal healers’ whose practice and influence in the mineral and gem world has taken on profound proportions? In recent years there has been a proliferation of the metaphysical and esoteric use of minerals and “crystals” supposedly for the enhancement of health and the treatment of disease. Mineral and gem shows are becoming increasingly dominated by “crystals” for healing purposes. Crystal healing practitioners use terms like 'energy' and they use it to cover anything that they can't explain any other way - such as 'energies unknown to science'. Do the claims of ‘crystal healers’ stand up to scientific scrutiny or is ‘crystal healing’ just another fashionable pseudoscience amongst a plethora of New Age hocus-pocus? Skeptics may be puzzled by the ready tendency of human beings to accept claims without sufficient evidence.
The late great Carl Sagan (1995) warned that there are “already many signs that modern culture may be on the verge of abandoning science for mysticism, and thereby sliding back almost without noticing it into superstition and the darkness that engulfed our demon-haunted world for thirteen centuries after the fall of Rome”. There also appears to be accelerated growth in anti-science in modern culture says renowned, skeptic, Paul Kurtz (2010) “It is paradoxical that today, when the sciences are advancing by leaps and bounds and when the earth is being transformed by scientific discovery and technological applications, a strong anti-science counterculture has emerged”
The rise of ‘New Age Science’ in recent years appears to govern the media which is filled with gobbledygook such as: tarot cards, quack medicine, magic waters, palm reading, UFO abduction, crystal healing, telepathy, astrology, conspiracy theories etc.... the list goes on and on. ‘New Age Movement’ literature in bookstores has grown to such an extent that books on the subject(s) outnumber books on science by a ratio of 10:1 (Hawkins, 2010). One possible reason for the proliferation of the ‘New Age Science’ may be that anyone can conjure up yet another madcap theory with absolutely no scientific evidence to support their theory and gets a cult following. In recent years, particularly with the rise of the New Age movement, myths concerning the healing powers of crystals have been introduced to society. Crystal healing practitioners claim to use ‘crystal energy', ignoring the fact that 'energy' has a very precise meaning in science. And they use it in an all-encompassing way to cover anything that they can't explain any other way - such as 'energies unknown to science'. Proponents claim that the healing properties of crystals rely on 'energy' that crystals are supposed to give off and that this energy exerts elusive influences on the body, realigning the body’s 'energy' into more harmonious, natural and healthy patterns (Willis, 2010). Here’s a quote from one of the many ‘Crystal Healing’ web sites [5.] giving an explanation on how to ‘select’ and ‘use’ a crystal for healing. “Crystal therapy involves the use of precious semi precious stones. These stones hold positive energy and act as a conduit for healing from the practitioner to the recipient. The stones also generate a healing vibration that heals on all levels, physical, spiritual, mental, emotional. A stone can be placed on the part of the body you would like to heal. A stone can also be placed on acupressure points. Generally therapists use quartz for physical healing amethyst for spiritual healing and rose quartz for emotional issues. There are many other crystals which carry a very specific healing vibration. They can pin-point complex healing issues & bring about healing & balance”
So, we are lead to believe that crystals allegedly affect the emotions and can be used not only for physical healing, but for emotional problems as well. Moreover, the claim goes further in boldly stating that crystals not only help with self-expression, and if that is not all …… creativity, meditation, AND the immune system! These claims are extraordinary. None of these assertions is backed by any scientific evidence – we just have to have faith and believe it! Extraordinary claims require extraordinary evidence. Everything about these claims should be skeptically examined and a demand for validation and verification be sought from the claimant. However, the burden-of-proof lies with those making the claim! Science has not identified any energy that could possibly be the healing energy claimed by crystal healers. Some crystal healers claim that the energy responsible is the piezoelectric effect, which is known to science. The piezoelectric effect can only be generated with a crystal that has been sliced into a thin section at specific orientations to the crystal axes and most types of crystals that crystals healers use cannot generate a piezoelectric effect anyway. Crystal healings may offer some assistance to some ailments, particularly emotional or psychological disturbances, but these healings are achieved as psychosomatic responses rather than through any direct effects from the properties of a crystal (Hawkins, 2010). The ready tendency of human beings to accept claims without sufficient evidence is wholly evident in the ‘New Age Movement’ and this includes ‘crystal healing’. Customers purchasing crystals from crystal healers often completely misunderstand the nature of what 'energy' means. In this way the customers are convinced, because the “effects” of the “energy” sounds good, without actually knowing anything about it and they take the word that the sellers are telling the truth and let’s not forget it’s good for sales. You can hang a tourmaline crystal around your neck, place quartz under your pillow, drink your mercury-laced cinnabar elixir and say it's providing health-giving energies, or 'cleansing energies' - whatever you please. What is being claimed has no scientific basis at all.
Many minerals species are potentially toxic - there are about 200 known radioactive minerals that contain uranium, thorium, or both elements [6.] and a large number are made up of heavy metals such as lead and mercury as in galena and cinnabar, respectively. I was horrified to hear a crystal healer practitioner announce with grand authority that realgar (an arsenic sulphide mineral, typically bright red in colour) can be used as an ‘elixir’ to promote a youthful appearance by boiling the mineral in water and drinking the water afterwards! “The red colour will vibrate with the root chakra!” she pronounced. Well I wonder how many of her customers were pronounced dead after drinking such a concoction!
As a scientist and a collector of minerals, I am unsympathetic to ‘crystal healing’ because it actively debauches the scientific enterprise, more so the disciplines of geology and mineralogy. And, even though all crystal healers and mystics will stand up and shout that “crystal healing works!” is not evidence that it does. Crystal Healing belongs in the same category as pink unicorns, Santa Claus and the tooth fairy. As modern culture is seemingly abandoning science and reason and accommodating mysticism there is an even greater need to question the validity of claims by following basic scientific methods of observation, independent testing, rational deduction, and verification by means of abundant evidence. We need to fight the misuse of science and praise the real wonder of science and avoid the ‘New Age’ taking us into a new ‘Dark Age’.
Quartz crystal from Rosh Pinah mine, Namibia. Photograph:A.Fraser
Cluster of clear quartz crystals (7 cm) from Rosh Pinah mine. Photograph:A.Fraser
References:
1. Sagan C. (1995). “The Demon-Haunted World - Science as a Candle in the Dark” (New York: Random House, 1995).
2. Kurtz P., (2010), “Exuberant Skepticism”, Prometheus Books, page 61
3. Hawkins C., “Crystal healing does it work?” http://www.helium.com/items/435008-crystal-healing-does-it-work (date accessed: 24 Dec 2010)
4. Willis P., “The Correx Archives” http://www.abc.net.au/science/correx/archives/crystal.htm (date accessed: 24 Dec 2010)
5. Donaldson R., http://www.helium.com/items/224162-crystal-healing-does-it-work (date accessed 29 Dec, 2010)
6. McGraw-Hill Science & Technology Encyclopedia: Radioactive Minerals http://www.answers.com/topic/radioactive-mineral (accessed 31 Dec, 2010)
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