From Sea Urchin Spines to Crystals: Adventures in early Mineral Identification

The science of mineralogy progressed rapidly during the late 18th and early 19th centuries, but in earlier times, it wasn't always obvious if something was a fossil or a mineral.

To illustrate the point, here's an interesting Victorian specimen from the Cumbrian mountain of Skiddaw, once in the collection of the colourful character Charles Ottley Groom-Napier (1839-1894) via the dealer Friedrich Krantz of Bonn.

A Groom-Napier specimen of chiastolite from Skiddaw, his label referring to the invented Museum of Mantua and Montferrat (M&M)



James Sowerby (1806) recognised the elongate features seen in this specimen as andalusite var chiastolite crystals ("MACLE or Chiastolite"), but noted that J. Woodward had earlier (1729) thought that these were the spines of sea urchins ("A black slate holding in it great numbers of spinulae of an Echinus spatagus").

"Mr. Davey having in the summer of 1804 found this substance on the summit of Mount Skiddaw in Cumberland, I am indebted to him for the power of adding it to the British list; and we had supposed it entirely new to Great Britain, had not Professor Hailstone assured us that it had not escaped the great founder of that professorship, Dr. Woodward, who, however, according to the knowledge of his time, considered it as a petrifaction."


Close-up of a cross section through one of the chiastolite prisms in the specimen shown above


Woodward's 1729 description of the material as spines of sea urchins


Title page of Woodward's 1729 book on the Natural History of the Fossils of England


Sowerby's 1806 illustration and description of the Skiddaw chiastolite


This is an entertaining illustration of the progress in understanding in geology from the early 18th to early 19th centuries. In the present, the difficulty of distinguishing organic from inorganic fossils or pseudo fossils persists in the study of Precambrian rocks.


References 

Sowerby, J. 1806. British Mineralogy, volume 2. Taylor & co., London

Woodward, John (1665-1728), 1729. A Catalogue of the Foreign Fossils in the Collection of J. Woodward M.D. Part I.

Comments

Post a Comment

Popular posts from this blog

Stone axes from the highlands of Papua New Guinea

Image
The story of first contact in 1933 with the peoples of the central Wahgi Valley in the Papuan highlands is a remarkable one. An unsuspected group of thriving stone-age cultures came to the attention of the outside world when the Leahy brothers first flew over the area and later reached it on foot. Tribal men carried elaborate stone axes and this contact with extant stone-age cultures provided fascinating insights on how their stone tools, such as axes and adzes were hafted. The available evidence was collated in Burton's (1984) Thesis at the Australia National University, on "AXE MAKERS OF THE WAHGI: Pre-colonial industrialists of the Papua New Guinea highlands." I saw a number of these old axes during a visit to the highlands near Mount Hagen in October 2018 (see the Paiya chief photograph below). The area of that journey is shown in the google Earth image shown below. The upper Wahgi River valley with locations of Paiya Village, Mount Giluwe and Mount Hagen t...
Read more

Urban Civets of Kuala Lumpur

Image
I derive great pleasure from encountering wildlife in the wilds, but also enjoy observing wild creatures in urban settings, such as along the bayou that wanders through Houston, Texas. I was delighted to find that in one of the world's most spectacular urban environments, the surroundings of the Petronas Twin Towers in Kuala Lumpur, there is some fascinating wildlife to be observed with a little patience and awareness. I had seen tree shrews, squirrels and bats on morning walks in the park, but first came across the civets ("toddy cats") that live there on evening runs on the track that circles the park. From about 9:30 pm onwards as people leave the central part of the park, the civets make a start on their night time activities, sometimes alone, sometimes with a youngster or two. This is the Asian palm civet ( Paradoxurus hermaphroditus ), nocturnal omnivore, active both on the ground and in the trees. Petronas twin towers at night. The KLCC park  in front of ...
Read more

A Merovingian Croix Ancrée Tremissis, Sutton Hoo, and Declining Gold Content in the 7th Century Coinage

Image
In the recent Netflix film "The Dig" there is a scene in which Basil Brown's character shows a small gold coin, known as a tremissis, to Edith Pretty, confirming that the ship burial at Sutton Hoo is of Anglo Saxon age as he had previously suspected. A Merovingian tremissis found in Kent, 10 mm across 37 such coins, all from Merovingian Francia, were found at Sutton Hoo, associated with the remains of an elaborate purse. These coins have commanded a great deal of attention as a potential means to constrain the date of the burial. This is a highly imprecise process (the coins are not datable to within a range shorter than 16 years), relying on recognising issues associated with known rulers (5 coins), identifying the youngest of these (Theudebert II), speculating from there as to how much younger the undated coins may be, and then how much later the assembled group was deposited in the ship burial. The absence of locally minted coins in the group (the earliest were the Eas...
Read more