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Calcite

yellow calcite at rockhoundz.com.au
yellow calcite

Common as a massive mineral in limestone (which can be formed from the chemical precipitation of calcite as well as transformation of shell, faecal and coral material) and marble (regionally or contact metamorphosed into marble). It is a late-forming replacement mineral in many environments and found in most geologic settings.

Formula: CaCo3

System: trigonal

Colour: white, yellow, red, black…

Lustre: vitreous, pearly

Hardness: 3

Streak: white

Cleavage: perfect

Fracture: conchoidal

Impurities: Mn,Fe,Zn,Co,Ba,Sr,Pb,Mg,Cu,Al,Ni,V,Cr,Mo

Uses

construction material: marble and limestone blocks in buildings and crushed to produce cement and as an aggregate

agricultural: soil treatment and a high calcium food supplement for poultry and cattle

pigment: powdered, it becomes very white (white streak) and is used in paint manufacture

pharmaceutical: for the treatment of digestive ailments

acid neutralisation: in chemistry and industry, such as mining, for water amelioration and in mine safety (sprayed on to walls in coal mining to reduce the risk of explosion from coal dust)

optical: high grade calcite was used in WWII for production of gun sights

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Is this a Houndz tooth I see before me?

pseudotooth

I know what I want this to be.  I really, really, really want it to be a fossilised dinosaur tooth.

It won’t be because I never find anything cool.  Except for that one time in Cifton – but I had a lot of paleontologists pointing me in the right direction and then Scott Hocknell took it away and I never saw it again.

I found this when I was sorting a sample of our rocks from Roma.  They are an assortment from a lot of different deposits that have been washed down a river and there are bits of petrified wood, some chert, quartzite, sandstone, something that feels ‘soapy’ that needs to be identified and lots of other bits and pieces as well.

roma sorted

They’re an excellent sample to have for showing erosion of different types of rocks.  A lot of the pieces have been broken as well so you get a fresh face of the sample to compare with the weathered portion.  Becuase they all come from the same deposit now they are a good example of how sediments are transported by water and how conglomerate rock can be formed of rocks from very different geological formations.

They would be great for primary school kids who just like to feel and examine different rocks as well as interesting samples for a stereomicroscope session. I think I’m really onto something there because when our friend Vivi pinned this pin to Pinterest last week and it grabbed attention really quickly from homeschoolers and teachers.

They also lend themselves to sorting and classifying experiments.  Rock collections like these are a good introduction for biological classification lessons and good practice at identifying similar traits in different objects.

Keep an eye out here for activities using this sample.  In the meantime you’ll be happy to know they have the Angus Seal of Approval.

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Steaming Coal

Hi Angus the Rockhound here,

I’ve been sniffing around some coal recently (hence my lovely black nose) and thought I’d tell you about the coal we have in stock which is classified as steaming coal and comes  from the Clermont mine in Central Queensland.

Steaming coal is a high grade of bituminous coal but not as highly graded as anthracite (the highest grade of coal). Steaming coal was traditionally used for powering steam engines and locomotives due to it’s superior thermal output. The bituminous coal grade also includes thermal coal which is mainly used in energy production today and is the bulk of production at Clermont. You may have also heard the term ‘coking coal’ which is also a sub-category of bituminous coal and is lower in sulphur and phosphorous and used in steel production.

This specimen is an example of Permian coal, is dense, black (not brown) and displays typical bands of bright and dull material.

Think I’ll go find a steam train to hang my head out of, that sounds like good fun for a hound!