FMF - Friends of Minerals Forum, discussion and message board

[Bob Harman]

Perhaps I should have started my postings with examples of simple quartz geodes, after all they are the basis of all the others with the secondary minerals upon the quartz. Ordinary quartz geodes are found by the millions in south central Indiana. Novices and casual collectors most commonly collect rather ordinary examples with little collector appeal or value to the more experienced collectors. Like with all field collected mineral specimens, it takes a bit of searching and luck to find truly top quality or unusual examples.
These 3 large examples, all from locations in Monroe County Indiana, represent higher quality and more unusual finds. They appear much better in person with more 3 dimensionality and more contrasting areas than pictures can show.

I will be posting more hi quality and unusual examples of quartz only geodes in the coming weeks and months.

[Matt_Zukowski]

Do you do anything special when you break open and then trim these geodes? How do you get them looking so good?

[Bob Harman]

HI MATT, Thanks for looking! So while I am now slowing down, when I was actively field collecting, I had to open many many examples to find the few that look like this.

Those that are still in surrounding matrix usually are fresh and don't need much except mechanical trimming with a splitter. Those examples like the just posted 3 quartz geodes, also did not need anything done except to open them as they were found whole and unbroken. If they had been iron stained or otherwise dingy, they would have only made our garden or been wholesaled. I do have lots of nice examples (huge big collection to the dismay of my wife, but no one else!) I only display and photo the very best of my examples that usually did not need much cleaning or prep attention. CHEERS.....BOB

[GneissWare]

[Bob Harman]

Of course this forum is primarily about minerals, but here is something a little different.

In Indiana where geodes might be found there are localities primarily in Monroe and Washington Counties that have mineral replaced fossils. Often, the original invertebrate fossil is easily recognized and now completely replaced by silica. Quartz replaced fossils; silicified or geodized fossils as they are called. As my pictures show, they can be hollow, with crystals in the cavity, or solid. These invertebrates are Mid-Mississippian age or about 425 million years old. They are quite common if you know where to look and are sought after by both fossil and Midwest mineral collectors.
This is distinct from minerals associated with fossils like the calcites in clams from Florida or the vivianite associated with Bolivian fossils, these examples represent complete mineral replacement of the fossil. They are similar to pyritized fossils.

[Bob Harman]

About 1963, when most quarries were open to weekend collecting, fluorite was discovered in the May Quarry (Fort Wayne Sand and Gravel Quarry) near the city of Fort Wayne in Allen County Indiana. Within weeks, the quarry was overrun by collectors and shortly thereafter most unauthorized collecting was stopped. Now only clubs, with management permission, gain occasional access to the quarry.
This example has several crystals in a small vug. The largest crystal measures about 4.5cm x 3.0cm x 3.0cm. Those collectors familiar with these examples can tell them from many similar Ohio quarry crystals. Over the years I have been shown a couple of examples with accompanying white bladed celestine claiming to be from Fort Wayne. Not true as no celestine has ever reliably been reported from this quarry. All fluorite with celestine comes from NW Ohio quarries.
The last time I collected in this quarry was with a 2008 club field trip. No one found much of anything. Then upon driving back to the quarry office to check out, we passed Volkswagen size boulders lining the gravel road to the office. They had been there for years. Checking them out, one had voids filled with similar cubes of fluorite crystals. We had a front end loader help break up the boulder and we went home with several nice specimens.

[Bob Harman]

In Indiana quartz can do strange and interesting things, much like pictures of quartz from many worldwide locations. These 2 examples, from the Harrodsburg road cuts in southern Monroe County show interesting crystal patterns.

[Bob Harman]

Over the years one of the steadiest and most prolific of high quality calcite producers has been the Berry Materials Quarry in North Vernon Indiana. Several pictures of North Vernon calcites have already been pictured on the site before this one.

[Bob Harman]

A very large (21 cm) and heavy Harrodsburg road cut geode collected about 11 years ago. This example is interesting in that it has a large isolated 8 cm rhombohedral calcite and a nearby isolated single 4.7 cm Baryte crystal. The translucent/transparent Baryte crystal is color zoned with micro marcasite inclusions. The area of interest in this example was suggested for culling out from the rest of the geode, but, too date, has been kept intact.

[Bob Harman]

Casual and weekend geode collectors in Indiana and other geode locations throughout the Midwest most commonly find "field and stream" geodes. This is the name given to those geodes that long ago have weathered out from the limestone matrix and are now found loose in the stream beds and plowed farm fields. The vast majority of these are weather worn, dingy, with corroded and degenerating secondary minerals in the cavity. Only an infrequent example is fresh inside. Experienced collectors shy away from these examples, but you commonly see them offered for sale at roadside stands and Midwest regional rock shows.

[Bob Harman]

Two geodes from the Monroe Reservoir spillway locality. The cm ruler is for scale showing that these examples can be quite small or quite large and heavy.
The larger example shows bright multicolored dolomites (pearly pink at 6 o'clock, orange yellow at the 5 and 7-8 o'clock positions and additional scattered bright brick red groupings elsewhere) along with a couple of terminated calcites and small intergrown Barytes, all on quartz.

[Bob Harman]

This 13cm - 14cm geode with a 10cm cavity is superficially similar to the previous example, but there are several important differences. The calcites in the previous example were of rhombohedral crystal type while this example has intergrown scalenohedral crystals, several of which are nicely terminated. Also these crystals have many visible marcasite inclusions while the previous example had calcites free of inclusions. Finally, there is no visible Baryte in the current example.

[Bob Harman]

While several secondary minerals are very common in quartz geodes, there are a number of rarely found secondary minerals. One of these is fluorite. Few examples exist and these seem to only be found in Harrison County examples as I have never heard of or seen a reliable example from any other Indiana county.

[Bob Harman]

I have exhibited at the Cincinnati Ohio show for about the last 8 years or so. For those who have attended this show, it is one of the larger US Midwest regional shows with many hi quality displays. Some years I have one case, some years 2 cases. One of my favorite topics has been the large and colorful calcite on dolomite geodes of Washington County. These have always been well received and, for persistent collectors, the roadcut has been a steady producer of display quality examples. These pix are of my 2011 case and the second of my 2 cases for newer finds at the 2015 Cincinnati show.

[Bob Harman]

In previous posts I have shown varieties of quartz in Indiana geodes. While common quartz crystal tips and microcrystalline quartz as the variety chalcedony are extremely common in geodes, finding an Indiana double cavity geode with a dividing septum with crystalline quartz in one cavity and microcrystalline quartz (chalcedony) in the other cavity seems exceptionally uncommon. One can only imagine under what formation conditions these 2 cavities with their respective crystals came to be.