Mica. When you see it in the ground or in a miner's hand for the first time, you know you've seen it in some shape or form before.
That's because mica is used extensively in several industries making lots of different consumer products.
As the child held up a large flake of ruby mica it clicked – the glistening tone was familiar. I had seen it before in cosmetic products.
Koderma district in India's Jharkhand Province has the world's largest mica deposits, according to the British Geological Survey.
It is mined extensively and yet, as far as we can tell, all of the mining here is illegal. The miners have no protection whatsoever.
We found children as young as six working at the mines. Child labour is prohibited under Indian law.
India produces more than 60% of the world's mica, but official figures tell their own story.
In 2015 India officially produced 19,000 tonnes of mica. But it exported 140,000 tonnes. Illegal production accounts for the huge discrepancy.
The illegal mines are run by cartels that make huge profits. By comparison, the mine workers earn a pittance and their work is extremely dangerous.
They dig deep into the earth, but there is no shoring up in the mines, so cave-ins are commonplace.
It's estimated that between five and 10 children die in the mines each month.
The number of adult fatalities is higher, but 90% of the deaths are never reported because of the unwelcome attention they might bring.
Many of the mines are deep in forests that are designated conservation areas.
Bureaucracy and competing laws prevent the Indian government from legalising mining – and so it goes on unchecked and unregulated.
Mica is in vogue in make-up because it's a natural product and its extraction is supposedly environmentally friendly. But mining it is anything but people-friendly.
India produces most of the world's mica. More than 75% of India's mica production is illegal.
All of which means it's impossible for the cosmetics industry to guarantee that illegally produced mica is not contained in the make-up sold worldwide. It's hardly a pretty picture.