Saturday, November 7, 2009

Jonathan Ertman: Maryland's Mr. Hunting Hill Garnet

Jon Ertman's nickname, "Maryland's Mr. Garnet," recognizes him as the premier aficionado, collector, and dealer to specialize in the grossular garnets from Hunting Hill Quarry in Rockville. Hunting Hill garnets may well have become Maryland's best known and most sought after contribution to the mineral kingdom. Jon's role with them has evolved over the 37 years since he moved with his family as a pre-teen from upstate New York to Rockville. Already a rockhound, he found his way the several miles from his new home to Hunting Hill in a matter of days.

Jon surmises that he's collected at Hunting Hill a couple hundred times. "Before OSHA," he recalls, " you could just sign a waiver at the gate to go in and collect." Today the quarry grants access only by pre-arrangement at specified times exclusively with clubs and groups that carry insurance. Jon is an active member of both the Montgomery County Mineral Society and the Northern Virginia Mineral Society, which share Hunting Hill as their most popular field trip destination. No other Maryland locality yields such a wide variety of minerals, 69 at last count. Hunting Hill is the only Maryland locality for many of these species. Some, such as pokrovskite and xonotlite, rarely occur anywhere else in the world.

Jon also takes pride in his suites of minerals from such no longer accessible Northern Virginia localities as Centreville Quarry, Bull Run Quarry, Luck Quarry, Chantilly Quarry, and Goose Creek Quarry. His collection also holds an enormous quantity of worldwide minerals. They dominate the inventory he sells at regional swaps and shows, although he emphasizes that every mineral in his collection is for sale.

Notwithstanding, Jon's Hunting Hill grossular garnets reign supreme. Displays such as pictured at left are prominent in his sizeable basement. Hundreds of smaller pieces, including plenty of thumbnails, fill flats lining the wall. The crystals typically ocur in a serpentinite-rodingite matrix and sometimes associate with very attractive light green clinochlore crystals. Of all the Hunting Hill garnet pieces in Jon's collection, his favorite is the one pictured at right. For aesthetics and quality, he sees it as representing the best of a classic genre. He'll sell it for $1000. If that's too much for the budget, plenty of very attractive smaller pieces go for less than $10.

Jon has sent some of his Hunting Hill garnets to Thailand for faceting. He charges about $80 a carat for these cut stones and is in no big hurry to sell them. Yours truly may have been among the first to get in on this one. Pictured at right is my wedding ring, in the center of which a Hunting Hill garnet that Jon collected has replaced the original diamond. At present, it's one of but a very few jewelry items anywhere to feature such a stone.

However unusual my ring, I have yet to see any jewelry bearing Patuxent River agate. Maryland's legislature chose this alleged manifestation of silicified dinosaur bone a few years ago as the State's official gemstone. Confident that most Maryland jewelers, geologists, and members of the rockhound community agree with him, Jon Ertman proclaims they should have picked Hunting Hill garnets.

Jon can be reached at

1 comment:

  1. My opinion (for what it is worth) is that there are threee worthy candidates for state gemstone:

    1.) Grossular Garnet
    2.) Smokey Quartz
    3.) Williamsite

    There are spectacular examples of cut gemstones for all three.

    Jeff Nagy