Some crystals appear to be twinned according to the albite law
. Electron microprobe analyses of these crystals show they are essentially pure albite ([sim][Ab.sub.98][An.sub.01][Or.sub.01]), containing approximately 0.24 weight % SrO.
In cavities it forms glassy, colorless, milky to transparent, tabular crystals up to 7 mm, twinned on the albite law
. It is nearly always associated with abundant quartz, gudmundite and dolomite, often with stibnite, and occasionally with pyrrhotite or berthierite.