Ludlow Diamond, a Rare and Unique Fluorescent Specimen from Southern California

Contributed by: Chris Clemens
minID: 89E-RMG
Date: Apr 17th, 2026
Locality: Ludlow (Stagg), San Bernardino County, California, USA (See on Mindat)
Size: 6.5 x 6.3 x 9.1 cm
Weight: 427 g

Description:
These unique and interesting fluorescent specimens are known as "Ludlow Diamonds", and were collected from an isolated occurrence in the Mojave Desert, in the Cady Mountains of San Bernardino County, near the town of Ludlow, California. Briefly, the proposed formative process is a three-phase sequence of events:

1.) Initial crystallization of scalenohedral calcite crystal containing lead and manganese activators, resulting in bright orange/red fluorescence.
2.) Deposition of non-fluorescent manganese oxide coating on the crystal growth surfaces, resulting in dark cross-sectional outlines; and
3.) Formation of additional calcite, absent of lead and manganese activators, that encased the original fluorescent calcite scalenohedron within a larger mass of colorless and weakly-fluorescent calcite.

When the resulting formation is cleaved, a diamond-shaped cross section of the original fluorescent calcite crystal is revealed within a larger colorless groundmass. (Robbins, Fluorescence, Gems and Minerals Under Ultraviolet Light, 1994). Sadly, the collecting site was reportedly obliterated by blasting decades ago and specimens of Ludlow diamonds are exceedingly rare today.

Second set of 4 images:Two different views of a second Ludlow Diamond specimen. This piece consists of a colorless calcite cleavage rhomb containing a dark-colored and brightly fluorescent partial Ludlow diamond. Images showing fluorescence under short wave UV (254 nm) at left, and corresponding photographs taken under visible light at right. The size of this specimen is 62 x 40 x 30 mm. Of historical interest, this piece was collected by Thomas Warren, a pioneer of our hobby of fluorescent mineral collecting. Click on the gallery images for a larger view.

Third set of 2 images: This third, and smallest specimen, features a partial calcite cleavage rhomb containing a partial Ludlow diamond corner. Shown under short wave UV (254 nm) at left, and visible light at right. The size of this piece is 43 x 38 x 22 mm. Click on the gallery images for a larger view.

Originally posted by Chris Clemens on Nature's Rainbows in 2020.