This aesthetic thumbnail is composed of jackstraw crystals of brassy Millerite. The German specimens are noted for relatively strong crystals compared to the ultrafine hairs you often see, and this specimen contain several small sprays. The needles are brassy-gold with a good metallic luster, and the Millerites that rise up show particularly well. Sprays of Millerite are uncommon and highly sought-after, occurring from just a few localities worldwide in this quality. Most of these would date to the 1800s, and a good one is hard to obtain - especially as a competition quality thumbnail. Lindemann collection (purchased in Germany in the 1960s, if I recall correctly from Kay).