Editorial Feature

Ludlamite – Occurrence, Properties, and Distribution

Aug 29 2013

Ludlamite is a rare phosphate mineral that is named after Henry Ludlam, an English mineral collector from London, England.

Properties of Ludlamite

The following are the key properties of ludlamite:

Cell Data
- Space group: P2₁/a
- a = 10.541(5)
- b = 4.646(4)
- c = 9.324(5)
- β= 100°25.8 (1.0)'
- Z = 2.
Crystal Data
- Monoclinic
- Point group: 2/m
- As crystals, usually tabular {001}, showing {100}, {110}, {001}, {111}, others, to 9 cm.
- Granular
- Massive
- X-ray powder pattern: (ICDD 17-468).
- 3.96 (100), 2.765 (100), 2.543 (100), 4.91 (75), 2.990 (60), 3.74 (50), 2.387 (40).

Chemical Composition

Elements	Content 1	Content 2
FeO	49.22	50.18
P₂O₅	32.95	33.04
H₂O	16.12	16.78
MgO	0.96	-
insol.	0.57	-
Total	99.82	100.00

Optical Properties
- Optical class: Biaxial (+)
- Orientation: Y = b; Z ^ c = –67°
- Dispersion: r > v, perceptible
- α = 1.650–1.653; β = 1.669–1.675; γ = 1.688–1.697
- 2V(meas.) = 82°.

Estimated Properties

Electron density	Bulk density (electron density) = 3.13 gm/cm³ note: Specific gravity of ludlamite = 3.15 gm/cm³
Photoelectric	PE_Ludlamite = 9.27 barns/electron U = PE_Ludlamite x ρElectron density = 29.02 barns/cm³
Fermion index	Fermion Index = 0.01 Boson Index = 0.99
Radioactivity	Ludlamite is not radioactive.

How to Identify Ludlamite

Ludlamite can be identified in the field by its color variations of apple green, green, greenish white, light green, and even colorless. The mineral occurs with both perfect and indistinct cleavages in a semi-transparent form. It has a glassy lustre with white streak and huge granular structure. The density of ludlamite is 3.15 g/cm³ with a hardness of 3.5 – approximate to copper penny.

Global Distribution

Ludlamite is widely distributed in many countries. The key locations are listed below:

UK - Wheal Jane, Kea, Cornwall, England.
Germany - Hagendorf, Bavaria.
Japan - Ashio mine, Tochigi Prefecture.
Canada - Yukon Territory.
Bolivia - Morococala and Huanuni, Oruro.
Serbia - Stari Trg mine (Trepca), Kosovo.
USA - Palermo #1 mine, North Groton, Grafton Co., New Hampshire; Blackbird mine, Lemhi Co., Idaho; Dan Patch, Ferguson, Big Chief, near Keystone, Pennington Co., South Dakota; the Rapid Creek district.
Mexico- San Antonio mine, Santa Eulalia district, Chihuahua.
Brazil - Enio pegmatite mine, northeast of Galileia, Minas Gerais.

Occurrence of Ludlamite and Useful Mineral Association

Ludlamite occurs in compound granite pegmatites, which is a basic hydrothermal alteration product of earlier phosphates that are formed under reducing circumstances. It is often associated with minerals such as triplite, phosphoferrite, triploidite, apatite, triphylite, fairfieldite, siderite, whitlockite, and vivianite.