Selenite Crystals

Introduction

selenite crystals

One of the oldest known, yet still productive, mineral localities in the state of Ohio is the Selenite crystal locality along the West Branch of Meander Creek, 1/3 mile Southeast of Ellsworth, Mahoning Co., Ohio. Many would argue this to be one of the best world-wide localities for Gypsum crystals of this form.

Having been described on multiple occasions, as in Edward Salisbary Dana’s original textbook of mineralogy, the locality has been famous for producing sharp, well formed Gypsum var. Selenite crystals for nearly 200 years. However, despite being a world-known classic locality, the clay bank which forms these Selenite crystals is rarely visited by mineral collectors.

Several factors contribute to the lack of attention given this locality in recent years.

First, more easily accessible localities for similar crystals have been discovered in the last 50 years.

Second, this locality remains relatively elusive, having never been described with pinpoint directions to the exact location, leading some to believe that it is either closed or defunct.

Third, the muddy nature of the locality during the best collecting season is moderately uninviting. Also, the locality is positioned on multiple properties and permission to collect is difficult to secure.

Finally, a general disregard among many collectors for common and colorless minerals has resulted in a lack of demand for quality specimens from the locality.

In recent years, only the most serious mineral collectors have any appreciation for these classic specimens. However, it is the author’s belief that the Ellsworth location remains the best Ohio locality for this crystal form of Gypsum.

In 1821, the Ellsworth location was first noted by Benjamin Silliman in the American Journal of Science in an article on crystallized gypsum. However, it is likely that the location was well known in the area for many years prior to that publication. Since that time, the locality has been described on multiple occasions.

Perhaps the best of these descriptions appeared in Rocks and Minerals v.12, in 1937. The article by Gerald Greene relays several important pieces of information about the locality. His article speaks of a large group outing to the site and a conversation with one of the older residents of the area.

He relates the story that a bushel of perfect crystals were collected 50 years prior and sold for $40.00. The more interesting fact in his story, geologically speaking, is that due to erosion and land use, the actual exposure of the clay had moved since its first discovery. The place where the bushel of crystals had been collected was located approximately 100 feet from the locality he had visited in his collecting efforts.

The reason for this is evident. As the stream slowly carves its way into the side of the hill, soil slides occur along the face of the clay bank revealing fresh clay. Over time, these slides grow over with vegetation. In fact, a conversation with one of the older landowners revealed that, at one time, the “crystal beds”, as they are locally known, were revealed by as many as 6 slides in a 100 yard stretch of the creek.

However, there is currently only one large slide which reveals the clay bank. With this in mind, it seems highly unlikely, that the current slide is in the exact location of the first discovery.

clear crystals

Geology 

The area surrounding Ellsworth was once part of a Pleistocene lake, likely resulting from the retreat of the Wisconsinan glacier which covered much of Northern Ohio. This lake deposited beds of clay, silt, and gravel. Beneath these pleistocene deposits lie Pennsylvanian age shale and limestone beds.

A thin coal seam has been reported nearby, and is evidenced in the gravel bars of the West Branch of Meander Creek. The crystal bearing clay is generally bluish gray, however at the surface it is partially mixed with soil and is lighter tan in color. The actual bluish gray clay layer is soft and slightly moist. It is also very compact, nearly water tight and generally difficult to dig through.

If not for small sediments and vegetation, the clay would be very suitable for sculpture or pottery. In the photo to the right, the thickness and tenacity of the clay are evident by a small hole, less than 50 cm across and 30 cm deep, which was dug for Selenite crystals.

More than one hour was required to carefully dig this small hole with a rock pick. However, this one area yielded several sharp Selenite crystals. Notice the clear pick marks remaining from working the stiff clay.

 

Mineralogy

The only mineral at this locality of interest to collectors is Gypsum. However, there are a few other minerals in the area which possibly led to the creation of the Selenite crystals. First, small amounts of Pyrite have been reported from the shale beds surrounding the coal. This is possibly the origin of the Sulfur for the Gypsum crystals. Small amounts of Limestone above the shale are theoretically the source of the Calcium.

It has been hypothesized that ground water movement along with seasonal evaporation formed the crystals. In addition, it is believed that these crystals are still forming in the clay. In fact, in dryer times of the year, the gypsum crystals appear to be sharper and larger. It is not clear whether the Gypsum crystals can grow from Calcium and Sulfur ions already in the clay or only through hydration and evaporation of local ground water.

An attempt to prove this by growing crystals in clay removed from the locality has thus far been inconclusive. Siderite concretions containing Sphalerite, Barite and Calcite have also been reported and observed in the vicinity of this locality. It is possible, that concretions containing the same minerals may occur in the shale beds beneath the clay at this locality. However, these minerals only occur as small masses and are not of specimen quality.