THE 'BLUE STONE' BOULDER, LOUTH, 

 LINCOLNSHIRE. 



W. HAMPTON. F.C.S-, and H. WALLIS KEW, F.E.S., 

 Hanley. Louth. 



The Louth ' Blue Stone ' is a subangiilar boulder of a blue-black 

 colour, about 32 inches in height and about 145 inches in girth, 

 estimated to weigh from four to five tons, which has existed in 

 Louth for centuries, and now rests in the yard of the ' Blue Stone 

 Printing Office' in Mercer Row. 



This boulder is, doubtless, a natural monolith of glacial times ; 

 its surface, however, does not exhibit definite striae. Unfortunately, 

 its natural position is unknown, but considering its large size and 

 great weight, the presumption is that it was originally found in the 

 immediate neighbourhood of Louth. 



After preparing and examining a large number of microscopical 

 sections, we consider the stone to be a typical Dolerite. It consists 

 of crystals of Plagioclase felspar (Labradorite) ; Augite, very fresh 

 and in large crystals ; Titaniferous Iron ; a greenish-looking decom- 

 position product (which may or may not represent former Olivine) ; 

 and brownish stains, which are probably due to the oxidation of the 

 Iron. As the result of our examination did not exactly agree with 

 the conclusions arrived at by one who had previously examined the 

 stone, a section was submitted to Dr. Bonney, who says : — ' The slide 

 contains Plagioclase felspar, probably Labradorite ; Augite ; Iron 

 Oxide (Ilmenite) ; and a greenish mineral of secondary origin, 

 probably indicating the former presence of a ferro-magnesian-silicate. 

 The replacing mineral is so indefinite in its character that I can 

 hardly venture to give it a name. The structure of the rock is 

 " Ophitic." It is merely a question whether we should call the 

 rock a dolerite or a diabase. It is not a very typical diabase, but 

 is a shghtly altered dolerite. So practically your determination is 

 accurate. In Scotland there are many dolerites in this condition, 

 where one man would call them dolerites and others diabases.' 



Formerly standing at the corner of Mercer Row — the principal 

 street in Louth — this boulder became a great nuisance as a 

 rendezvous for loafers and idlers, on which account it was removed, 

 at a considerable expense, to the premises above-mentioned. These 

 premises were in old time a large county inn, of which the ' Blue 

 Stone' formed the material sign, and there is still in Louth a pubhc- 

 house, known as the ' Blue Stone Inn,' which has a rough 



