Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Large colorless crystals of Analcime are a great rarity although small transparent crystals are abundant. Faceted gems are extremely rare and seldom seen even in large collections. The hardness is marginal for wear, but the mineral has no cleavage and should present no difficulties in cutting.
| Data | Value |
|---|---|
| Name | Analcime |
| Colors | Colorless, white, gray, yellowish, pink, greenish. |
| Hardness | 5-5.5 |
| Fracture | Subconchoidal |
| Cleavage | Indistinct |
| Stone Sizes | Gems are nearly always colorless and less than 1-2 carats when faceted. Large crystals from Mt. Ste. Hilaire are white but may have small facetable areas. Crystals in basaltic cavities in general do not exceed ¼ inch in size and are transparent. |
| Formula | NaAlSi2O6 · H2O |
| Crystallography | Isometric; good crystals are common, usually trapezohedra. Massive, granular. |
| Crystallographic Forms | |
| Refractive Index | 1.479-1.493 |
| Birefringence | None. Anomalous in polarized light. |
| Luminescence | Cream white in LW (Golden, Colorado). |
| Absorption Spectrum | Not diagnostic. |
| Pleochroism | None |
| Optics | Isotropic; N = 1.479-1.493. May show anomalous birefringence. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long |
| Luster | Vitreous. |
| Specific Gravity | 2.22-2.29 |
| Transparency | Transparent to opaque. |
| Phenomena | Chatoyancy. |
Optics: Isotropic; N = 1.479-1.493.
Occurrence: Secondary mineral in basic igneous rocks; also in sedimentary rocks such as siltstones and sandstones. Washington, Oregon, and California (Columbia Plateau area).
Houghton County, Michigan.
New Jersey: Watchung basalt flows.
India: Deccan Plateau.
Nova Scotia: Bay of Fundy area.
Mt. Ste. Hilaire, Quebec, Canada.
Also Scotland, Ireland, Iceland, Norway, Italy, Czechoslovakia, Germany, Australia.
Comments: Large colorless crystals of Analcime are a great rarity although small transparent crystals are abundant. Faceted gems are extremely rare and seldom seen even in large collections. The hardness is marginal for wear, but the mineral has no cleavage and should present no difficulties in cutting.
Name: From the Greek analkis, meaning weak, because of the weak electric charge analcime develops when it is rubbed.
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