Lepidolite
Lepidolite is a typical mineral found in lithium-rich pegmatites. Because it is mostly found as scaly aggregates, it is also known as "scale mica" (rin-unmo), and its English name is derived from the word for "scale." Other names include lilacite, lithium mica, and in China, it is known as "ding xiang zi" (clove purple).
Characterized by a thin, easily flaking, micaceous texture
Basic Information
| English Name | Lepidolite |
|---|---|
| Japanese Name | Lithia mica |
| Chemical Formula | K(Li,Al)3[(F,OH)2|(Si,Al)4O10] |
| Classification | Monoclinic system |
| Hardness | 2.5–4 |
| Specific Gravity | 3 |
| Transparency | — |
Characteristics & Trade Names
- Group name: A general term for trilithionite (Li>Al, Si>Al) and polylithionite (Al>Li, Al>Si) (previously considered independent minerals).
- Crystal form: While mica is monoclinic, it can take on a hexagonal prismatic crystal shape due to its similarity to corundum, resulting in pseudo-hexagonal twinning.
- Trade/Commercial names: Lilac Jade (same as the Chinese "ding xiang zi": dense, massive lepidolite).
Treatments, Similar Stones, Precautions & Related Info
Treatments: Dyeing (colored with purple dye), coating (synthetic resin coating for beads to prevent scratches).
Similar stones: Manganophyllite (purple due to Mn) or masutomilite, etc. (chemical analysis may be required for accurate identification).
Characteristics and precautions: Innumerable cleavage planes run perpendicular to the column, making it easy to split or peel into very thin sheets along those directions. This is because only those surfaces are bonded by intermolecular forces (very weak forces). Due to its low hardness and perfect cleavage, it lacks durability as jewelry and requires careful handling.
Related information: Pink aventurine (Quartz containing manganese-colored pink mica) is currently being marketed as strawberry quartz. Also, be aware that items containing Mn-rich epidote are sometimes sold under common names.
Related information: The radioactive isotope ⁸⁷Rb contained in the stone decays into ⁸⁷Sr, a property used to estimate the age of the stone's formation.
Note: Its low hardness and tendency to "flake easily" are fundamental traits. If using for accessories, ensure designs account for impacts, friction, moisture, and whether or not it is coated.