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<p>[QUOTE=&quot;AnYangMan, post: 4898042, member: 87271&quot;]Malachite appears in many shades of greens and forms! While its single crystals are almost never visible, especially on coins (It would be extremely cool), in contrast to the cuprite and cerussite crystals above which are large enough to identify with the naked eye, it is the mass of malachite that in&nbsp; some cases can be botryoidal. Often also called ‘swirly Malachite’; especially on the Vietnamese coin you can see why. There are various other minerals that have the same mineral-habit and that appear in the same manner on coins, including spertiniite (from a single Southern Song hoard), smithsonite (high zinc coins) and even cornwallite.</p><p><br /></p><p>A Botryoidal texture (from the Greek for &#039;Grapes&#039;, I guess you can see why) can for example happen when there is a small particle of some sort, sand or a rough (casting) surface, that has radial crystal growth around it; this forms a sort of globule. It is quite normal for coins and can be seen on the coin [USER=104887]@Broucheion[/USER] posted (and I think I see a globule or two on&nbsp; [USER=75496]@Carl Wilmont[/USER] ‘s coin). A sort of small semi-sphere, looks like a bubble. But on their coins you see a lot of malachite growth that was not around such a particle but just on the coin’s surfaces, meaning the botryoidal structure, or something very much like it but not as perfectly round, only shows up occasionally. On the two examples I posted, the same process happened, but just with a lot more radially growing botryoides. These then fuse together after they keep growing and voila, you have that bubbly texture that we call botryoidal! In reality the process is a lot more complex and has to do with the conditions in which the coin is deposited as well. The first example I posted is especially clear; you can make out all the little bubbly botryoides!</p><p><br /></p><p>Ps. I too am no expert chemist or geologist, but had the privilege of learning a thing or two from an expert chemist with a specialisation in bronze patination![/QUOTE]</p><p><br /></p>

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