reported a porous MOF, PCN-20 (Figure 9) with a twisted boracite
topology based on a designed planar TTCA ligand.
The witherite, calcite, fluorite, barite, linarite, barytocalcite and plumbogummite have never been beaten, mimetite from Dry Gill (the variety known as campylite) is unique, and the recent finds of boracite
from Boulby mine have set new standards for the species.
More than 230 different types of boron minerals are known in nature, but the number having commercial importance is limited to the following: tincal, colemanite, kernite, ulexite, pandermite, boracite
, szaibelyite and hydroboracite.
It is famous for producing the world's finest specimens of blue boracite
, as well as trembathite and hilgardite.
Also from the home country (der Vaterland, if you prefer) comes exciting news of an old locality coming again to life: Jordi Fabre has obtained a few specimens showing gemmy green boracite
crystals in matrix, found just this year in the Grona mine, Bernburg, Sachsen-Anhalt.
Occurrence: Associated minerals are: sylvite, halite, boracite
, anhydrite, magnesite and quartz.
Exciting recent discoveries include epidote and Japan-law twinned quartz from Pampa Blanca, Peru; danburite and boracite
from the Alto Chapare distr ict, Bolivia; vivianite and ludlamite from Morococala, Bolivia; cassiterite from Viloco, Bolivia; and new minerals from Chile including szenicsite, lemanskiite, cristelite, and gordaite.
Finally, on a visit to Hanau in April he purchased about 30 specimens for [pound]11 including a collection of agates, Luneburg boracite
, Bohemian garnets at 1 Ecu for 1 pound weight and a steatite after quartz at 9 Ecus, found near Bareuth, described as very rare and singular.
Fluorite and boracite
are excellent possibilities as each occasionally forms dodecahedra, and twinning about  is known.
He had also specimens of boracite
and hildegardite presumably found in 1991 at the Boulby Potash mine I see Mineralogical Record, vol.
The Boulby potash mine has produced some of the world's finest specimens of blue boracite
, ericaite and hilgardite.
Associated species include: drusy microcline, dolomite, talc, gypsum, danburite, pyrite, hematite, magnesite (in hexagonal prisms) and rarely boracite