Macraes+Gold

=Ask-a Geologist: Is it Gold?=

Wade brought these rock core samples from Macraes Goldfield into the Museum recently. Wade with his collection || A sample core with pieces of drilling equipment || End of a core, showing gold-coloured speckles on the right. || Dinolite microscope image of the speckles || =The Geologist's Answer....= The core is a greyish coloured type of greenschist. The bands of white colour are a mixture of quartz and calcite.(Calcite fizzes in dilute hydrochloric acid). The white minerals in the end cross-section are a mixture of calcite and possibly scheelite. The gold-yellow mineral is mostly flaky and very thin. It's streak is black. It gives off a sulphury smell with acid and, though it may contain traces of gold, it has no visible gold residue.
 * [[image:P1100510.JPG width="270" height="255" align="center"]]
 * [[image:P1100513.JPG]]
 * It is not gold. It is pyrite.**

It is sometimes called **"fool's gold"** because it looks like gold.
 * Pyrite** is the most common sulphide and occurs all over the world where it is often found as cubes.

A perfect cube pyrite from Spain [|Navajun pyrites] || A cluster of iron pyrites from South America. || Both gold and pyrite are gold-coloured and metallic and both can look flaky. But when you scratch a hard surface with gold, it leaves a **yellow** streak - pyrite leaves a **black** streak. Gold is a pure metal and doesn't react with acid. Macraes' pyrites contain sulphur and calcium so they fizz and give of a sulphury smell with acid.
 * We have two other pyrite specimens in the museum:**
 * [[image:pyritespain.jpg width="260" height="235"]]

Most of the gold found at Macraes Flat is microscopic. Find out how it is extracted.....
 * [[image:macraes3.jpg width="268" height="202"]] || == Discover more about Macraes Gold Mine ,,, ==

**[|An Online Fieldtrip]**
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