Some 500 minerals fluoresce. A twisted crystal, most famously Swiss quartz, which can occur in unusually flattened crystals twisted in corkscrew fashion. HBM The Handbook of Mineralogy, a handy reference series. HCl Hydrochloric acid, of great use for the removal of massive calcite or other carbonates, to expose hidden crystals. Sold diluted, as muriatic acid.
Examples are tourmaline and hemimorphite.
Herkimer diamond Quartz crystals found in the vicinity of Herkimer, New York. Hey's Hey's Mineral Index, a book useful for its inclusion of many old discredited names. Highgrade ore is exceptionally rich. To highgrade a mineral collection is to sort out the best specimens. Highgrading in the mining industry means either removing only the best ore or, more commonly, theft by miners.