What does it look like?
What is it?
Side by side, it’s hard to tell apart Malachite and it’s rarer ‘imposter’ mineral pseudomalchite – both are green, form a crystal that looks a bit waxy and grow in a rounded (or botryoidal) form. But diffract with an x-ray beam and the differences really reveal themselves.
Rather than an copper carbonate hydroxide, pseudomalachite is a copper phosphate hydroxide. And it isn’t that the phosphate atoms take the place of the carbon atoms – it’s a whole different crystal structure. Rather than forming the sheets of copper, oxygen and carbon atoms that malachite does – pseudomalachile forms more of a framework structure, as a result it is a harder mineral.
The way to tell them apart in the field is to drip a couple of drops of warm hydrochloric acid onto each rock – malachite will react, but psuedomalachite won’t.
Where did the structure come from?