64 MICHIGAN ACADEMY OF SCIENCE. 



Although our lime rock is the same formation there is a marked differ- 

 ence in the crystals from the different openings. The Davis street quarry 

 was worked to a "depth of 28 feet below the sidewalk. Dog-tooth spar 

 crystals were found abundantly and increased both in size and numbers 

 nearly to the depth of the excavation. They were found in cavities in 

 what are called "Geode Beds." In the deeper part of the pit the supply 

 of crystals suddenly stopped. These crystals (specimens shown) came 

 from that opening. I have at home two pieces of limestone, each about 

 14 inches long and inches wide, one with crystals as large as this one. 

 and the other with six or eight crystals of half this size, both imbedded 

 in a surface of pyrite crystals. These crystals may not be large for 

 other places but they are the largest we have found. 



Iron pyrites crystals were found common at Davis street but seldom 

 larger than ^ cubes. The variety Marcasite was found in much greater 

 <)uantity. I found one piece in the shape of a ball 1:} inches in diameter. 

 A piece of stone 4 feet long and 2^- wide was found covered with pyrite 

 cubes. I could have had it but it was too large for me. It is now doing 

 duty in a cemetery. De])osits of calcite or brown spar were found here 

 in larger pieces tlian in any oHier [»lace. One piece was nearly a cubic 

 foot contents. It is usually found as a nodule imbedded in tlie solid 

 rock. Sometimes it is found in Hakes which make up a vein through the 

 stone. In this quarry also I found these curious double-colored crystals 

 not found elsewhere. (Specimens exhibited.) 



In the lowest heading of this pit, 28 feet deep, I found several cavities 

 with the inside pitted instead of covered with crystals. I took out a few 

 of the holes (?) which are represented by this sample. At the Davis 

 street extension scalenohedrons were found in plenty, and here I found 

 a cavity with loose crystals — the only one discovered. The crystals were 

 imbedded in sand or clay, and had evidently fallen from the roof of the 

 openiug. There was so much outside earth iu the cavity that it was 

 useless to consider any of it as a residue of crystallization. In the open- 

 ing just below the dam nodules of calcite were found, but nothing worth 

 taking home. 



In the excavation for the filter in the bed of the river just above the 

 <iry water works, brown cubical crystals were found iu good numbers. 

 Mere I found caA'ities containing gypsum — lime sulphate instead of the 

 carbonate. Some of them, cavities as largo as my fist, had the surface 

 of the gypsum level. The holes were about two-thirds full, and the 

 h^vel surface indicated a deposit from solution. 



In stone near the upper end of the exposure I found a few cavities 

 lined with pyrites. Tliese are rare and I have seen only one other, which 

 was spoiled in taking out. 



Many valu.'i.ble specimens were found at the Taylor street quarry, but 

 ihat was abandoned and tilled before I came to the city, so I can only 

 repeat what I hear from others. I have broken more specimens in the 

 quarry than I ever took home with me, on account of the shaly nature 

 of the stone. However carefully I might line out my work the piece 

 would often break at right angles to my marks and the disturbance of 

 my temper. 



At the Myrtle street opening white and brown cubical crystals were 

 found. The white crystals were rare and were not found in other places. 

 Much iron pyrites was found here but in a decnrnjiosed condition. Joints 



