• Q1: I am in Grade 6 and I am doing a project on Silica as an earth science assignment. There is one section which I am having trouble finding information on. 'Where is Silica found in Australia and around the world, and what are the major mining methods?' I hope you can help. I wish I had found your web page sooner!

  A1: Silica is so common that you probably could go out into your backyard and dig some up. It is the chemical name for quartz sand, the usual sand found at Sydney beaches. It is mined at lots of places but perhaps the sand pits at Kurnell and near Richmond around Sydney are two of the main sites that serve the Sydney region. There are sand pits all over the country for use in concrete making . Silicon is the element and makes up a large proportion of the planet earth.

  
  
• Q2: Do we have quicksand in NSW? Are there shifting sands in deserts that act like quicksand?

  A2: Yes there are quick sands present where ever there is loose sand. The "quick" condition is only because the sand is loose, either in water or on the lee side of shifting sand dunes. It is generally not a permanent condition and may come and go depending on the vagaries of wind and water. The cause is that the sand grains are not in contact; they are separated by a film of moisture or are in a virtual air suspension.

  
  
• Q3: I am a seventh grade student in Florida, USA and I am learning about geologists. Could you tell me whether or not you enjoy being a geologist? What is the best (and the worst) part of the job? Do you have fun? Are your days interesting or boring. Thank you for any information you can give me about your career as a geologist. From the information I have found so far, it seems as though it would be an interesting job. Thank you for your help.

  A3: I have found that being a geologist has been very rewarding and always facinating and quite often surprising. I have been an exploration geologist looking for minerals, an engineering geologist involved with major construction projects like dams and tunnels, a marine geologist involved with coastal processes including erosion of the beaches, an environmental geologist looking at landslip, flooding and pollution. Each of these specialities have their own aspects, but all rely on a basic understanding of rocks, minerals and geological processes. The main drawback is that most geological work is done out in the boondocks; rarely in a nice airconditioned office, and not very often in a large town or city. Being an underground mining geologist can be more challenging and suited to people who can work under pressure. The best part is the variety: no two jobs are the same; and you are often out in the fresh air. If there are dangers eg from wild animals then you would usually be working as part of a group, even if only 2 people. Where there are no real hazards then you might very often find yourself working all alone.

  So you need to be a self motivator I am sure that you would find it an interesting career.

  
  
• Q4: My daughter is studying the Gold Rush and part of her term project requires her to map the gold mines here in Australia from the 1800 and now. Could you suggest a website that has this information easily and simply laid out please. Your time is appreciated, thanks.

  A4: I am afraid that there is no single website that I know of that gives a simplified coverage of the locations and details of the main gold mining sites in Australia since the 1800's. Mostly they are all terribly detailed, depicting the thousands of sites from which gold has been found.

  You could try Geoscience Australia in Canberra and AusIMM in Melbourne, or Gold Gazette as a last resort.

  However, I am sure that all that you need to indicate is that historically, the Kalgoorlie area in Western Australia, the Charters Towers area in Qld, the Ballarat-Bendigo area in Victoria, the Orange-Bathurst-Hill End area in NSW, and minor occurrences near Tennant Creek in the NT, were the main sites. More recently there has been a proliferation (litterally hundreds) of mostly small mines throughout Australia, but I am sure that you are not supposed to go down to that level of detail for any project. There are only a dozen or so really big new ones, eg Ernest Henry in QLD, several in the northern goldfields area (eg Bronzewing) of WA and the Olympic Dam mine in SA.. The details of production are probably too scattered for any meaningfull private discussion for a project.

  Hope that this helps a little.

  
  
• Q5: I am trying to put together a collection of flourosent minerals and was wondering where in NSW I would go to find such material? are the any "old mines" where there maybe samples?

  A5: There are a surprising number of minerals with fluorescent character. However, some fluoresce at long UV wavelengths, while others only do so at short UV wavelengths. Very few fluoresce at indiscriminate mixed UV light.

  The common ones are fluorite, scheelite, wolastonite, calcite and so on.

  There is no one location where you can obtain a range of fluorescing minerals; it will take perseverance and investigation to get a more complete listing of minerals and their required wavelengths, and whereabouts you might find them. The other problem is the type of UV light source you get.

  Hope this sets you off in the right direction.

  
  
• Q6: Can you tell me how satelite remote sensing of vegitation can help geologists determine possible locations of mineral? Does different vegetatation grow with certain mineral deposits or can certain mineral deposits affect the growing patterns of vegetation? Do you have a simple chart that I could look at that would tell me what minerals I might expect to find, say for example if gold or copper deposits were present. I am researching this topic for a remote sensing project. As you have probably gathered I am neither a geologist nor botanist and any help you could give would be thoroughly appreciated. Kind Regards.

  A6: Remotely sensed satellite data is used routinely by geologists to look for discontinuities in surface materials. This can be outcrops of rock or vegetation. On remotely sensed satellite data, long and thin continuous bands of large trees can often indicate a structural discontinuity such as a fault or joint in the rocks. Many mineral deposits are associated with faults and joints as they can be conduits of fluids that may carry mineralisation.

  Using satellite data to detect and interpret different patterns of vegetation that may be associated with mineral deposits is difficult because of the low spatial and spectral resolution of the data. However remotely sensed data that has been acquired from a plane flying at low altitudes (ie about 100m) such as the 'Hymap' system does have sufficient spatial and spectral resolution to identify a range of minerals such as goethite, hematite and gypsum and several vegetation end-members.

  In summary - using remotely sensed satellite data to map vegetation anomolies that may be associated with mineralisation is not currently routinely done. The satellite data can be used to locate structures such as faults and joints that may be associated with mineralisation.

  The 'Hymap' system does have the ability to map different types of minerals and vegetation. It may be possible to use this data to locate geobotanical anomolies that may indicate mineralisation.

  
  
• Q7: I was wondering how exactly the Sydney Basin was formed? Thank you in anticipation!

  A7: The Sydney Basin is a relatively long lived depositional basin that had a tectonic initiation probably back in the Late Carboniferous, and in which sedimentation probably continued right through until the late Jurassic. Mostly these days however, people are talking about the Triassic depositional time for the Narrabeen, Hawkesbury and Wianamatta Group sediments.

  The tectonic initiation was probably a result of either mild east-west directed compression or a "pulling apart" east-west tensional phase, allowing a linear north-south trending depression to form into which sediment was deposited, and with the result that the loading due to the weight of the sediment caused further subsidence, allowing further sedimentation, and so the cycle continued. Bear in mind that this is only a reconstruction - we are still sorting the tangle out.

  
  
• Q8: I recently received two haematite stones as gifts. I was wondering if you could tell me where they originate from, how they are made etc...

  A8: I am afraid that haematite (English spelling) is a very common mineral. It is one of the main ores of iron for steel making. Polished stones could literally have come from almost anywhere in the world. However, on the basis of its low value, I would suspect that to be economic for polishing it would have to be done in a very low wage country such as India or even China or Russia. However, this is only a guess. It could even have been done by an enthusiast in Australia ! Best specimens tend to come from the Hammersey Ranges of Western Australia.

  Hope that this does not disappoint you too much.

  
  
• Q9: I am intending to climb parts of the Warrumbungles. Would you please advise what rock type the spires/mountains/bluffs of the Warrumbungles are comprised of eg grantie, sandstone etc.? The minerals.nsw.gov website suggested the New England is comprised of a type of Granite. Thanks for your help.

  A9: Most of the spires in the Warrumbungles are the frozen plugs of old volcanic centres, or are the thin vertical dykes emanating from said centres, and as such are composed of a variety of basaltic rock types of various grades of crystallinity; some are porphyritic giving the appearance of a non-basaltic rock, while most are very fine grained.

  Much of the New England region is underlain by granites, but they are often very different both in type and age. Some individual masses are extensive in area, while many are quite localised, so if you look at the maps you will see a whole range of coloured bodies, each one representing an individual granite mass. Good climbing.

  
  
• Q10: I am 7 years old. I have a class project on careers and I'd like to know more information about being a geologist like what training I need, qualifications,what equipment I need. I want to be a geologist because my dad is a geologist (he helped me write this). If you have any information to help me that would be great!

  A10: I do not know of any simple or ready source of information for your project. A simple statement of what a geologist does could be : "a geologist studies rocks to determine the characteristics, eg shape of the mass and its position in the sequence, and the individual minerals that make up the rock, both to determine what the rock type is, what the rock is made of and what it might contain in the way of valuable things eg oil or gold. Also, what the rock might contain in the way of fossils or other features which could enable the geologist to tell what sort of conditions the rock was formed in and what has happened to it since. Some clues also allow a geologist to work out how old the rock is. Each of these types of investigation are usually done by specialists who have special names such as a palaeontologist who looks for and interprets fossilized remains, geochemists who study the chemical make up of rocks and minerals, petrologists who look in great detail at the contents of rocks and minerals. Oil (petroleum) geologists obviously look for oil , while mineralogists look at the nature of the minerals, usually the valuable ones, in rocks.

  To become a geologist in Australia usually requires a degree from a University, and depending on what sort of specialisation you are interested in will determine the type of experience or special skills that your potential employer will require you to have. Usually you do not need much in the way of equipment - a hammer, compass, and magnifying glass, plus a rucksack to carry home the specimens that you have collected while working in the field. You would also have to wear good boots and somne semblance of protective clothing to protect against sun burn and any other inhospitable elements. Your employer (unless you were an independent consultant) would provide any expensive items such as a microscope or geophysical equipment. In some countries you might need to be part of a team because of the presence of wild and dangerous animals or extreme weather conditions eg in Antartica or the Sahara desert.

  There are so many different fields of specialisation and places of work that it is impossible to list them all.

  Cheers and I hope this gives you some ideas for your Dad to fill in the details.

  
  
• Q11: What is the geology of Lake George and the area surrounding it, near the ACT? University level Thank you.

  A11: We do not provide answers for Uni projects for which you are supposed to do some research and reading, so I hope that this is not your motive in asking.

  Lake George is an internal drainage basin formed by a fault scarp on its west. The lacustrine sediments in its floor are mostly of Tertiary to Recent age, and are several tens of metres thick in places. The sand dunes at its northern end are of Recent age.

  The former AGSO (Canberra) has done a lot of drilling and investigation of the geology of the Lake area over the years and I believe has a publication condensing all the data and theories, which any Uni Geology School library should have a copy of it if you want to follow up any particular aspects. The former NSW Deparment of Main Roads (now RTA) would have done some drilling along the scarp zone during its investigations for the re-building of the highway. Cheers and all the best.

  
  
• Q12: I have a 6 year old boy, who is very keen to know more about the rock and minerals. What would you recommend? I am thinking of a plate of rock and mineral samples in accordance with its origin, sedimentary, volcanic or metamorphic etc. If I want to buy these , what are the procedures and where can I get them?

  A12: I would agree that a set of minerals is probably the best starting point until he can enjoy picture books and read the descriptions.

  Unfortunately our Department no longer prepares sets of specimens, having left it to commercial sellers to handle the business, so I really cannot help you much in your search. However, in the phone book there are listed some of the gem and mineral clubs and sellers of mineral specimens, who would be a good starting point. Often there is a seller at local street markets, and there are a couple of shops in the Rocks area that seem to sell specimens, but whether they have sets, I do not know.

  Try Australian Fossickers Club - NSW and Our Fossicking Information Page as a starting point.

  Good luck.

  
  
• Q13: I am a Wilderness Park Officer. We are putting a comprehensive compendium on the natural history together. On the geology section, I struggle with the different 'times' eg Jurassic, Devonian, Cambrian... I used these terms in the animal evolution as well. Would you have a short, easy to understand description and year figure on the different stages, eg Devonian age, 200 million years, continents started to dry up and the Gondwana super continent started to drift apart??? It would be much appreciated if you could put me in the right direction (internet site??) Kind regards.

  A13: There is no simple geological time scale, mainly because people are forever arguing about the individual time spans and the relative overlaps in the fossil record. However, in Australia we mostly follow the AGSO line (now called Geoscience Australia). I suspect that they will have a version of the geological time scale on their site. failing that you could try the Australian Museum in Sydney or even your own states museum in Perth.

  Many of the simplified books and encyclopaedias will have a time scale of sorts, depending on where and when the book was compiled and what aspect they are trying to describe.

  Our Maps and Publications

  Geological Time Scale Example: University of California - Berkeley, Museum of Paleontology

  Good Luck!

  
  
• Q14: Someone one showed me a rock the other day. Not sure exactly where it is from but, generally the Sydney Basin sowewhere. I am studying civil engineering so they expected me to know exactly what it was. But I didn't know and I hope you can help me. Basic description is a grey sandstone type appearance with small clayey seams. For all I know, that's exaclty what it is, but it could be some wierd igneous or something. Also, just out of interest, the rocks around Kiama at the blowhole etc, what are they?

  A14: From your description I would guess that it is a laminated fine grained sandstone, with the thin clayey seams being grey shale, but it is really a bit of a best guess, and it really could be something quite different.

  But I do not think that it is likely to be a volcanic or igneous rock unless it was either very hard or somewhat weathered which had enhanced the internal banding.

  All of the rocks around Kiama and especially at the blowhole are volcanic. The unit at the blowhole is a lava of the latite (basalt) type, although it is showing considerable colour variation due to both weathering and the complex of flows present.

  
  
• Q15: Could you please tell me the geological history of Lake Mungo, and the evidence for this geological history? What fossil evidence is there for past aquatic life? Thank you!

  A15: As best I know I would try the NSW NPand WS site for information on Lake Mungo, as it is too young for geology, it having dried up about 15,000 years ago.

  As an alternative you could try the geomorphology aspects from the Geography side of research. Sorry.
  

• Q16: What was the "cause and effect" of Mesozoic sedimentation in the Ouachita Mobile Belt Region?

  A16: Ouachita Mobile Belt region is not in Australia. "Ouachita Mobile Belt extends from the subsurface of Mississippi to Texas. The Ouchita Mts. and Marathon Mts. are exposed areas of shallow-water clastic and carbonate sediments deformed by compressive forces generated as Gondwana collided with Laurasia." according to the University of Illinois at Chicago database. Please refer to US resources for further information. Cheers!
  

• Q17: Do you know what causes the "hot rock" deposits in coal measures such as occurs at Drayton Coal in the Hunter Valley. Is it sedimentary rock under pressure or the result of high level igneous activity? Is this a similar case at Burning Mountain south of Armidale?

  A17: The "hot rock" at Drayton is believed due to an underlying high level igneous body that is still cooling down, but as no one has drilled down to it yet, we are only surmising.

  Sometimes a sedimentary rock unit with a high pyrite/marcasite/pyrrhotite content can start to oxidise as it is weathered and in the process of forming sulphuric acid, it can give off a lot of heat. This is the origin of spontaneous combustion in some "dirty" coals.

  The burning mountain at Wingen is caused by the burning of an underground coal seam that is believed to have been ignited due to spontaneous combustion, possibly a bushfire or lightning, that occurred about 5000 years ago. Cheers.
  

• Q18: I've just dug some soil pits on my property which is 16km north of Kyogle northern NSW. The soil is a chocolate soil and in one of the pits I have found some small rocks approx 30cm diametre. They look a bit like a thunder egg, when they a broken open they have either a black core or a red core. The red centre is more common. The centre can be crushed between finger and thumb but the outside shell has to be broken with a hammer. Some of the rocks where fractured during excavation which is why I decided to break open some of these rocks. Could you please tell me what they are and maybe how they are formed. Thankyou very much for your time.

  A18: I suspect that what you have uncovered is either a re-deposited lateritised soil horizon or a ferruginous nodular horizon derived from a weathered basaltic agglomerate. Either is possible in your area, although the laterite is the most probable, despite the large size of the concretions, and would have been derived as a result of weathering from the underlying Grafton Formation or Walloon Coal Measure shales, which are of mid to late Jurassic age.

  However, I am only guessing, as it could simply be a highly weathered boulder conglomerate. The chocolate coloured soil is however, a bit of a puzzle as it usually reflects a rich alluvium from a stream flood plain, but such would be unlikely to contain nodules. One last idea is that it is a completly weathered coaly horizon that contained some large pyrite nodules that have been oxidised during the weathering process.

  The actual concretions or nodules may be a groundwater developed effect or a weathering feature or of a depositional origin, but again I am only guessing. I am assuming that they are not chunks of fossilized wood.

  I am sorry but I cannot be any more specific than that from your description. Cheers
  

• Q19: What roof slate material would be available nearest to Sydney?

  A19: The old quarry at Goulburn is the closest (and only) location to Sydney containing material even vaguely comparable to the imported Welsh roofing slates, but the quality is relatively poor and very variable and there was always a lot of wastage. There are no other places that I know of that were worked for roofing slates, although Mudgee is a well known source of flagging stone slate.
  

• Q20: What type rocks do you get around Sydney and where are they used?

  A20: Sydney is in the middle of an ancient sedimentary basin, which stretches from Newcastle to Wollongong and west to Lithgow. As such it mainly contains primary sedimentary rocks of the sandstone type with lesser shale, siltstone and occasional conglomerate and coal. The only real exception are the basaltic volcanic necks and dykes and some rare larger intrusives, such as at Prospect, Dundass and Minchinbury. As a result of probably a long period of weathering in eons past, there are minor surface deposits of ferruginous and lateritic materials, and some relatively impure kaolin.

  One variety of sandstone, originally probably high in iron carbonates, gives rise to ferruginous sandstone or (the missnomer), "ironstone" during weathering.

  The sandstones are all dominantly quartzose, with clay matrix material and commonly cemented with silica and iron carbonates, and frequently make good building stone for monumental masonry construction, while the shales and siltstones are used for earthenware pottery such as bricks, pipes and roofing tiles. There were quarries for sandstone and brick making clay/shale scattered throughout the metropolitan area during the earlier growth stage of the City, but most quarry sites are on the present cities outskirts. The abundance of sandstone has meant that Sydney is endowed with good quality construction sand, although much of it is located in environmentally sensitive sites such as beaches and dunes.

  
  
• Q21: What's the source of huge magnetic high 15k west of Gosford? and has anyone drilled it?

  A21: This feature is caused by magnetic rock at considerable depth. Preliminary estimates indicate that the top of this body is greater than 4 kilometres. Consequently it has not been drilled.

  Another similar magnetic anomaly occurs 20 kilometres to the west and is thought to be similar source material. Coincident gravity data are sparse but do not suggest that a significant gravity anomaly is associated with the magnetic anomalies. This suggests that the source material is some type of non-mafic igneous intrusion.

  
  
• Q22: What can you tell me about oil seepages east of Terrigal?

  A22: There were a number of reports of oil seepages from the general Terrigal area over a long period of time. This was the basis of the geologically (in)famous Terrigal No1 petroleum drillhole sunk during the mid 1960s by a famous character - John Streven. It is now recognised that oil seeps occur from certain units in the lower Narrabeen Group succession, and in fact some gas flows with condensate have been obtained in the Wilton-Camden area.

  
  
• Q23: What can you tell about the basement rock under Sydney?

  A23: The Sydney Basin is areally quite large so you would not expect the basement rocks underlying it to be uniform, either in terms of rock type or age of the rocks.

  Correlation and extrapolation from Magnetic and Gravity surveys, and from mapping of exposed rocks at the margins of the basin, indicate that the basement to the Sydney Basin are variously : Carboniferous age volcanics and possible granites in the north, while to the south the basement is Devonian sedimentary and volcanic units, and to the west the basement is another suite of mostly Devonian sediments and volcanics with some intrusives.

  Under Sydney City, the basement is at a depth of about 2000m, and is probably of Carboniferous age volcaniclastics.

  
  

Have you got a general geological question not covered by the FAQ or a rock sample and you don't know what it is?, want to know if that black stuff you dug up in the garden is coal?, well this page gives you the opportunity to ask a Geologist.

Provide as much information as possible with your question, for example where you found the rock, and if possible a scanned photograph of the rock. Questions should also be accompanied with your details so that "Bill the Geo" knows at what level he should address his answer. In return we will provide you with as much information as possible to help improve your knowledge of the fascinating world of Geology.

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Send a message to our resident expert Bill the Geologist and he will do his best to answer your enquiry directly.

Alternatively, you can also refer to Minfacts, easy-to-read information sheets for students and others interested in minerals and mining.