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Hi there, I manage to 'borrow' these rocks from a quarry that I dive occasionally. I've given them a good scrub and soaked them for a bit. Im just wondering if these funny colours in the rock are some sort of ore that will leach into the water. Is there anything I should do, like boil them -...

I thought i'd convey my results following an evening of measuring small amounts of liquid and dripping tiny bottles. I decided to 'calibrate' my NO3 test kit for two reasons: 1. I have a mistrust in things that are 'cheap' i.e. not £100's 2. I must be colour blind because I can't tell if I have...