FMF - Friends of Minerals Forum, discussion and message board

[Bob Harman]

Another large well displayed Indiana example that some dealers wish to have the area of calcite and barite crystals culled from the remainder of the geode and offered as a non-geode specimen.

[Bob Harman]

Another nice example of a well displayed large Indiana geode with a dominant calcite aesthetically surrounded by several groups of dolomite, all on quartz. The quartz crystals in this example form nice free form growths.

[Bob Harman]

A recently collected large and well displayed example with calcites on quartz. From my private lands site in Washington County.

[Bob Harman]

When I go field collecting at this time of the year, I expect to see freshly exposed examples associated with rock falls resulting from the recent freeze/thaw episodes. So it has been for years.
These examples, from the Indiana route 56 road cuts in Washington County, were high up on the rock wall and, unfortunately, unable to be retrieved intact. The several pix of the larger example show a large 18+ cm specimen with large calcites upon bright red dolomite. If it had been collected intact and cleaned up well, it would have been a show stopper in a display case, but over several years, it fragmented and finally fell in multiple small fragments.

You can see the very porous dolostone matrix fragmenting with slices falling off the wall. If you are unlucky, one of the larger pieces might fall like a guillotine cutting or slicing off your wrist. Since these pictures were taken, both high quality examples became history; unfortunately, not all high quality examples can be successfully collected.

[Bob Harman]

The field and stream geodes from Washington County Indiana tend to be large and very large. This example is on display as part of a small geode collection in the geology building at Indiana University. As you can see it is immense in size and weighs 347 lbs. These have very limited collector appeal, only making good yard rocks or decorations such as this one. Interestingly, these very large examples tend to have very small central cavities and be dingy or rusty stained inside.

Several of the geodes on the poster are from my collection.

[Bob Harman]

An example with more collector interest is this quartz geode containing a dominant and nicely placed and nicely terminated 6.5 cm baryte crystal nestled near the "back" of the quartz lining. A smaller partial crystal can be seen in the lower right area of the cavity

[Bob Harman]

Found about 15 years ago, this aragonite consists of numerous white spiky needles on decayed ferroan dolomite in a geode cavity.

[Bob Harman]

Finding fresh geodes in the limestone matrix is the way to go for dedicated collectors and finding "field and stream geodes" in creek beds is, for novices, very common, but explaining how the geodes weather out of the limestone to wind upon the creek beds is not so apparent. Finding geodes that are in the natural process of weathering out of their matrix is quite unusual. Here is one collected about 2005.

[Bob Harman]

Bladed baryte on quartz

[Bob Harman]

An intergrown group of baryte crystals with dolomite and calcites at the 5 - 6 o'clock position.

[Bob Harman]

Collectible examples marcasite on quartz or dolomite are quite uncommon in Indiana.

[Bob Harman]

Another well displayed baryte with multicolored dolomite groups on quartz

[Bob Harman]

Several more examples of calcite. Left example is on quartz, the center example is on chalcedony variety of quartz and the example on the right is on dolomite. The unifying theme with these is that the calcite crystal nearly fills the cavity of each specimen, but never-the-less are terminated with no contact points on the visible surfaces.

[Bob Harman]

Another well displayed baryte cluster with a number of well terminated blades radiating outward from the cluster's center. Similar to the previously posted example with accompanying dolomite, but this example has only a small area of minor calcite and no marcasite or smythite inclusions in the baryte crystals. Acquired in 2010.

[Bob Harman]

When I started posting all these examples, I was undecided whether to post them in the "my collection" thread as some others do or in the thread of "a mineralogical trip thru the states of the USA". It was a toss up so all the photos and descriptions wound up into this thread of Indiana minerals.

This example was collected at a small road cut in March of 2013. The road cut along Indiana route 37, North of Bloomington, is now an extinct locality as the road is currently being upgraded to Interstate 69 and the cut was leveled and contoured just within the last several months.