Rose quartz, if I don’t miss my guess, but I’m no geologist….
I had never thought of managing a garden to increase insect life in general (not just butterflies—sorry KW—for example). Actually it’s just a smokescreen for managing for biodiversity and native species.
No more privet. No more nandina. No more Acer palmatum. Sadly, no more daffodils or pansies, both blooming now….