Tidying. I'm most familiar with open-cut mining.

@@ -16 +16 @@
-<xref type="ant" seq="2535680">坑内掘り</xref>
+<xref type="see" seq="2535680">坑内掘り</xref>
@@ -17,0 +18 @@
+<gloss>open-cut mining</gloss>
@@ -19 +19,0 @@
-<gloss>open-cut or open-air (strip) mining</gloss>

https://ja.wikipedia.org/wiki/露天掘り
English xref is "surface mining"
Note the failure to translate "strip mining" or "open-pit mining" as *types* of 露天掘り。（Instead, their characteristics are defined alongside the original English terms)
一方、使用する重機で区別することもある。Strip Mining(en)はドラッグライン（固定したクレーン）を使う方法であり、Open Pit Mining(en)はシャベルカーとダンプカーを使う方法である。Strip Miningは効率がいいが、設備投資がかかり、広い設置場所が必要である。Open Pit Miningはシャベルカーを使うため、斜面の多い場所では便利である[1]。


特集 - ゼロからわかるマイニング
https://www.hitachicm.com/global/ja/corporate/publicity/magazine/2019/vol128/feature/
そして、鉱石を掘る方法には、大きく分けて「露天掘り」と「坑内掘り」がある（右図参照）。

https://americanmineservices.com/types-of-surface-mining/#:~:text=Surface mining refers to the,on the minerals being extracted.
Surface mining makes up a huge percent of mining projects. Surface mining refers to the removal of the terrain surface to access minerals underneath. In particular, surface mining is used to retrieve sand, gravel, stones, coal, iron and other metals.

There are five recognized types of surface mining, each with specific variations depending on the minerals being extracted. These include strip mining, open-pit mining, mountaintop removal, dredging and highwall mining.

Lead gloss should definitely be "surface mining". This is a common, industry standard term. 

"open-pit mining" is a *type* of 露天掘り.  English seems to have a lot of fine distinctions for types of surface mining that Japanese lacks(see last reference).  I have not found any good gloss, for example, for "open-pit mining", "strip mining", etc. 

reverso is a mix of all the glosses now listed:
https://context.reverso.net/translation/japanese-english/露天掘り

We already have an entry for 
露天掘り炭鉱
open-pit coal mine; open-cut coal mine

I think I've included everything needed here, but see also comments on 坑内掘り, also edited.

@@ -15,0 +16,4 @@
+<xref type="ant" seq="2535680">坑内掘り</xref>
+<xref type="ant" seq="2535680">坑内掘り</xref>
+<gloss>surface mining</gloss>
+<gloss>open-pit mining</gloss>

@@ -6,0 +6,4 @@
+</k_ele>
+<k_ele>
+<keb>露天掘</keb>
+<ke_inf>&io;</ke_inf>