These are extremely rare in any quantity, as most crystals over 10mm have inclusions of some kind. We are very fortunate to network with a small group of local miners right here in NY. I know many of them personally and have developed great relationships over the years. These amazing double terminated Crystals are what started it all for IVC back in 2006. Herks are harder than normal quartz at around 7.5. These double terminated Crystals are some of the best in the World.
The work that goes into hand mining these is demanding on every level. The sorting & cleaning requires hours of painstaking work. Thus the prices these amazing crystals command. Most never see bulk quantities of this quality, the number of pockets one must mine requires an entire season of mining, if not more to acquire.
Herkimer Diamond Quartz Crystals come from a small area of Central Upstate NY, primarily from Herkimer County and the Middleville & Herkimer, Little Falls area, also St. Johnsville & Fonda. This is the 3rd hardest rock in the world, Dolostone / Limestone.
There are look alike crystals from other locations, Pakistan, Mexico, China, that also use the Herkimer Name. These are similar but not the same. The location of the crystals should be used instead of riding on the popularity of the much rarer quartz crystals from NY.
For help with measurements : 25.4mm = 1"
5 ct (carats) = 1 gram