Hopper and Skeletal Herkimer Diamonds

These odd looking quartz crystals from the Herkimer mining district are found in every deposit.  They have an important message to share with us about the growing environment for Herkimer diamonds..

The Significance of Hopper Growth

The slide show starts with a slde of “examples of hopper growth”.  These are NOT from the Herkimer district (the sldes after will be!).  They are shown to share with the viewer images which might be familiar. Also, knowing that the conditions which make hopper crystals can be seen in other minerals helps us to understand the processes. There is a photo of hopper salt crystals. These are formed when the water evaporated rapidly thus increasing the salt content dissolved in the water (called salinity).  When the conditions are right, the solutions will get to the point where the salt can no longer stay dissolved.  That is when crystals will begin to form and then grow. Most authors speak about saturation (amount of quartz dissolved in solution) at very high levels (called super saturation) as being the governing factor for hopper type growth.  But in the Herkimer district it is likely the hydrocarbons and kinetic energy, also played a role.

In the slide are illustrations of how hopper and skeletal crystals were formed - its a competition between crystallization on the edge versus on the face.  The presence of hopper growth patterns is indicative of rapid growth rate. The slide show contains many different features seen in association with hopper development across the Herkimer Mining District.

 Terminology Several different terms are applied by collectors to this form of Herkimer diamond - elestial, jacare quartz, negative manifestation quartz, skeletal, negative skeletal quartz, fenester quartz, window quartz,  cavernous quartz and hopper.  In the mineral kingdom the term “skeleton” frequently refers to the process of solving the crystal and leaving a skeleton behind, although the shape of a full hopper looks quite similar. Skeletal is the term most commonly used in labeling Herkimer diamonds with any hint of hopper step like growth.  It may not be the proper term.  A more appropriate label would be “Herkimer diamond with hopper growth”. If the growth is preserved inside the crystal, and you can see it, then “Herkimer diamond with window to hopper growth”. The window can be described in the label as open, partial, or closed. The labeling is further complicated by over growths, secondary event features, spiral tendencies, and parallel growth all contributing to complex hopper growth.

Slide show contributors:Example Name……

The new discovery, to be announced on July 16 and 17, will change how we understand hopper growth in the Herkimer Mining District.