Stepped Calcite - Rensselaer Quarry, Rennselaer, Indiana
Contributed by: Chris Clemens
minID: HRW-TG0
Date: May 23rd, 2026
Locality: Rensselaer Quarry, Pleasant Ridge, Jasper County, Indiana, USA (See on Mindat)
Size: 84 x 74 x 85 mm
Weight: 510 g
Description:
This is a rare and unique fluorescent calcite specimen from the Rensselaer Quarry, Pleasant Ridge, Jasper County, Indiana that shows a very unusual stepped crystal habit. This piece features a large grouping of intergrown, translucent, golden honey colored, highly modified, stepped rhombohedral calcite crystals. As is typical for the Rensselaer location, this specimen is coated with dark bitumen. The crystals also contain bitumen inclusions. This specimen is at its best under midwave UV, with the bitumen showing yellow-tan fluorescence which contrasts nicely against the pink response of the underlying calcite.
The Rensselaer Quarry, also known as the Pleasant Ridge Quarry, is located approximately 3 miles east of Rensselaer, Indiana. The quarry is a former open pit producer of dolostone aggregate but is now closed and flooded with water. Natural bitumen commonly permeates the dolostone and often coats the mineral specimens collected there.
The bitumen coating shows a yellow-tan response while the underlying calcite fluoresces pink under midwave UV (302 nm). Note that the pink fluorescence of the underlying calcite is only visible in areas of the specimen where the bitumen coating is thin or has rubbed off. The bitumen shows a similar fluorescent response under all UV wavelengths, but the calcite is only weakly fluorescent under short wave (254 nm) and long wave (365 nm) UV.
Originally posted by Chris Clemens on Nature's Rainbows in 2022.
Summary of luminescence responses:
Calcite (Mindat) (RRUFF)
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Pink
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Yellow