boracite | colourless or white | vitreous | 7–7½ | 2.9–3.0 |
borax | colourless to white; grayish, bluish, greenish | vitreous to resinous | 2–2½ | 1.7 |
colemanite | colourless; white, yellowish, gray | brilliant vitreous to adamantine | 4½ | 2.4 |
inyoite | colourless, becoming white and cloudy after partial dehydration | vitreous | 2 | 1.7 |
kernite | colourless | vitreous | 2½ | 1.9 |
ludwigite | dark green to coal black | silky | 5 | 3.6 (lud) to 4.7 (paig) |
priceite | white | earthy | 3–3½ | 2.4 |
sussexite | white to straw-yellow | silky to dull or earthy | 3–3½ | 2.6 (szai) to 3.3 (suss) |
tincalconite | white (natural); colourless (artificial) | vitreous | | 1.9 |
ulexite | colourless; white | vitreous; silky or satiny | 2½ | 2.0 |
name | habit or form | fracture or cleavage | refractive indices | crystal system |
boracite | isolated, embedded, cubelike crystals | conchoidal to uneven fracture | alpha = 1.658–1.662 beta = 1.662–1.667 gamma = 1.668–1.673 | orthorhombic (isometric above 265 degrees C) |
borax | short prismatic crystals | one perfect, one good cleavage | alpha = 1.445 beta = 1.469 gamma = 1.472 | monoclinic |
colemanite | short prismatic crystals; massive | one perfect, one distinct cleavage | alpha = 1.586 beta = 1.592 gamma = 1.614 | monoclinic |
inyoite | short prisms and coarse crystal aggregates; geodes; drusy crusts; granular massive | one good cleavage | alpha = 1.492–1.495 beta = 1.501–1.510 gamma = 1.516–1.520 | monoclinic |
kernite | very large crystals; fibrous, cleavable, irregular masses | two perfect cleavages | alpha = 1.454 beta = 1.472 gamma = 1.488 | monoclinic |
ludwigite | fibrous masses; rosettes; sheaflike aggregates | no observed cleavage | alpha = 1.83–1.85 beta = 1.83–1.85 gamma = 1.97–2.02 | orthorhombic |
priceite | soft and chalky to hard and tough nodules | earthy to conchoidal | alpha = 1.569–1.576 beta = 1.588–1.594 gamma = 1.590–1.597 | triclinic(?) |
sussexite | fibrous or felted masses or veinlets; nodules | | alpha = 1.575–1.670 beta = 1.646–1.728 gamma = 1.650–1.732 | probably orthorhombic |
tincalconite | found in nature as a fine-grained powder; physical properties are given for artificial pseudocubic crystals | hackly fracture | omega = 1.461 epsilon = 1.474 | hexagonal |
ulexite | small nodular, rounded, or lenslike crystal aggregates; fibrous botryoidal crusts; rarely as single crystals | one perfect, one good cleavage | alpha = 1.491–1.496 beta = 1.504–1.506 gamma = 1.519–1.520 | triclinic |